package service

import (
	"container/heap"
	"context"
	"errors"
	"fmt"
	"hash/fnv"
	"log/slog"
	"math"
	"sort"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"github.com/Wei-Shaw/sub2api/internal/config"
	"golang.org/x/sync/singleflight"
)

const (
	openAIAccountScheduleLayerPreviousResponse = "previous_response_id"
	openAIAccountScheduleLayerSessionSticky    = "session_hash"
	openAIAccountScheduleLayerLoadBalance      = "load_balance"
	openAIAdvancedSchedulerSettingKey          = "openai_advanced_scheduler_enabled"
)

const (
	openAIAdvancedSchedulerSettingCacheTTL  = 5 * time.Second
	openAIAdvancedSchedulerSettingDBTimeout = 2 * time.Second
	// ponytail: cap probes added when cost ordering expands configured Top-K;
	// use bulk acquisition if a measured workload needs a higher ceiling.
	openAIAccountSelectionProbeLimit = 64
)

const (
	openAIQuotaHeadroomNeutralFactor           = 0.5
	openAIQuotaHeadroomSecondaryLowRemain      = 0.10
	openAIQuotaHeadroomSnapshotStaleAfter      = 8 * time.Hour
	openAIUpstreamCostNeutralFactor            = 0.5
	defaultOpenAIOAuthSchedulingRateMultiplier = 1.0
)

type cachedOpenAIAdvancedSchedulerSetting struct {
	lowUpstreamRatePriorityEnabled bool
	oauthSchedulingRateMultiplier  float64
	enabled                        bool
	stickyWeightedEnabled          bool
	subscriptionPriorityEnabled    bool
	lbTopKOverride                 int
	weightOverrides                map[string]float64
	expiresAt                      int64
}

type openAIAdvancedSchedulerRuntimeSettings struct {
	lowUpstreamRatePriorityEnabled bool
	oauthSchedulingRateMultiplier  float64
	enabled                        bool
	stickyWeightedEnabled          bool
	subscriptionPriorityEnabled    bool
	lbTopKOverride                 int
	weightOverrides                map[string]float64
}

var openAIAdvancedSchedulerSettingCache atomic.Value // *cachedOpenAIAdvancedSchedulerSetting
var openAIAdvancedSchedulerSettingSF singleflight.Group

type OpenAIAccountScheduleRequest struct {
	GroupID                 *int64
	Platform                string
	SessionHash             string
	StickyAccountID         int64
	StickyPreviousAccountID int64
	StickyWeighted          bool
	SubscriptionPriority    bool
	PreserveStickyBinding   bool
	PreviousResponseID      string
	PreviousResponseCanMove bool
	UseUpstreamTokenCost    bool
	RequestedModel          string
	RequiredTransport       OpenAIUpstreamTransport
	RequiredCapability      OpenAIEndpointCapability
	RequiredImageCapability OpenAIImagesCapability
	// RequireCompact is only for legacy /responses/compact capability filtering
	// and compact_model_mapping; native remote compaction v2 leaves it false.
	RequireCompact bool
	ExcludedIDs    map[int64]struct{}
}

type OpenAIAccountScheduleDecision struct {
	Layer               string
	StickyPreviousHit   bool
	StickySessionHit    bool
	CandidateCount      int
	TopK                int
	LatencyMs           int64
	LoadSkew            float64
	SelectedAccountID   int64
	SelectedAccountType string
}

type OpenAIAccountSchedulerMetricsSnapshot struct {
	SelectTotal              int64
	StickyPreviousHitTotal   int64
	StickySessionHitTotal    int64
	LoadBalanceSelectTotal   int64
	AccountSwitchTotal       int64
	SchedulerLatencyMsTotal  int64
	SchedulerLatencyMsAvg    float64
	StickyHitRatio           float64
	AccountSwitchRate        float64
	LoadSkewAvg              float64
	RuntimeStatsAccountCount int
}

type OpenAIAccountScheduler interface {
	Select(ctx context.Context, req OpenAIAccountScheduleRequest) (*AccountSelectionResult, OpenAIAccountScheduleDecision, error)
	ReportResult(accountID int64, success bool, firstTokenMs *int)
	ReportSwitch()
	SnapshotMetrics() OpenAIAccountSchedulerMetricsSnapshot
}

type openAIAccountSchedulerMetrics struct {
	selectTotal            atomic.Int64
	stickyPreviousHitTotal atomic.Int64
	stickySessionHitTotal  atomic.Int64
	loadBalanceSelectTotal atomic.Int64
	accountSwitchTotal     atomic.Int64
	latencyMsTotal         atomic.Int64
	loadSkewMilliTotal     atomic.Int64
}

type openAIAccountLoadPlan struct {
	allCandidates             []openAIAccountCandidateScore
	candidates                []openAIAccountCandidateScore
	staleSnapshotCompactRetry []openAIAccountCandidateScore
	selectionOrder            []openAIAccountCandidateScore
	candidateCount            int
	topK                      int
	loadSkew                  float64
	includeOverflowFallback   bool
}

type openAIAccountLoadSelectionAttempt struct {
	result              *AccountSelectionResult
	selectionOrder      []openAIAccountCandidateScore
	candidateCount      int
	topK                int
	loadSkew            float64
	compactBlocked      bool
	noCompactCandidates bool
	err                 error
}

func (m *openAIAccountSchedulerMetrics) recordSelect(decision OpenAIAccountScheduleDecision) {
	if m == nil {
		return
	}
	m.selectTotal.Add(1)
	m.latencyMsTotal.Add(decision.LatencyMs)
	m.loadSkewMilliTotal.Add(int64(math.Round(decision.LoadSkew * 1000)))
	if decision.StickyPreviousHit {
		m.stickyPreviousHitTotal.Add(1)
	}
	if decision.StickySessionHit {
		m.stickySessionHitTotal.Add(1)
	}
	if decision.Layer == openAIAccountScheduleLayerLoadBalance {
		m.loadBalanceSelectTotal.Add(1)
	}
}

func (m *openAIAccountSchedulerMetrics) recordSwitch() {
	if m == nil {
		return
	}
	m.accountSwitchTotal.Add(1)
}

type openAIAccountRuntimeStats struct {
	accounts     sync.Map
	accountCount atomic.Int64
}

type openAIAccountRuntimeStat struct {
	errorRateEWMABits atomic.Uint64
	ttftEWMABits      atomic.Uint64
}

func newOpenAIAccountRuntimeStats() *openAIAccountRuntimeStats {
	return &openAIAccountRuntimeStats{}
}

func (s *openAIAccountRuntimeStats) loadOrCreate(accountID int64) *openAIAccountRuntimeStat {
	if value, ok := s.accounts.Load(accountID); ok {
		stat, _ := value.(*openAIAccountRuntimeStat)
		if stat != nil {
			return stat
		}
	}

	stat := &openAIAccountRuntimeStat{}
	stat.ttftEWMABits.Store(math.Float64bits(math.NaN()))
	actual, loaded := s.accounts.LoadOrStore(accountID, stat)
	if !loaded {
		s.accountCount.Add(1)
		return stat
	}
	existing, _ := actual.(*openAIAccountRuntimeStat)
	if existing != nil {
		return existing
	}
	return stat
}

func updateEWMAAtomic(target *atomic.Uint64, sample float64, alpha float64) {
	for {
		oldBits := target.Load()
		oldValue := math.Float64frombits(oldBits)
		newValue := alpha*sample + (1-alpha)*oldValue
		if target.CompareAndSwap(oldBits, math.Float64bits(newValue)) {
			return
		}
	}
}

func (s *openAIAccountRuntimeStats) report(accountID int64, success bool, firstTokenMs *int) {
	if s == nil || accountID <= 0 {
		return
	}
	const alpha = 0.2
	stat := s.loadOrCreate(accountID)

	errorSample := 1.0
	if success {
		errorSample = 0.0
	}
	updateEWMAAtomic(&stat.errorRateEWMABits, errorSample, alpha)

	if firstTokenMs != nil && *firstTokenMs > 0 {
		ttft := float64(*firstTokenMs)
		ttftBits := math.Float64bits(ttft)
		for {
			oldBits := stat.ttftEWMABits.Load()
			oldValue := math.Float64frombits(oldBits)
			if math.IsNaN(oldValue) {
				if stat.ttftEWMABits.CompareAndSwap(oldBits, ttftBits) {
					break
				}
				continue
			}
			newValue := alpha*ttft + (1-alpha)*oldValue
			if stat.ttftEWMABits.CompareAndSwap(oldBits, math.Float64bits(newValue)) {
				break
			}
		}
	}
}

func (s *openAIAccountRuntimeStats) snapshot(accountID int64) (errorRate float64, ttft float64, hasTTFT bool) {
	if s == nil || accountID <= 0 {
		return 0, 0, false
	}
	value, ok := s.accounts.Load(accountID)
	if !ok {
		return 0, 0, false
	}
	stat, _ := value.(*openAIAccountRuntimeStat)
	if stat == nil {
		return 0, 0, false
	}
	errorRate = clamp01(math.Float64frombits(stat.errorRateEWMABits.Load()))
	ttftValue := math.Float64frombits(stat.ttftEWMABits.Load())
	if math.IsNaN(ttftValue) {
		return errorRate, 0, false
	}
	return errorRate, ttftValue, true
}

func (s *openAIAccountRuntimeStats) size() int {
	if s == nil {
		return 0
	}
	return int(s.accountCount.Load())
}

type defaultOpenAIAccountScheduler struct {
	service                *OpenAIGatewayService
	metrics                openAIAccountSchedulerMetrics
	stats                  *openAIAccountRuntimeStats
	grokFreeQuotaGateCache sync.Map // key: int64(accountID), value: grokFreeQuotaGateCacheEntry
}

type openAISelectionProbeBudget struct {
	acquires  int
	rechecks  int
	attempted map[int64]struct{}
	limited   bool
}

func newOpenAISelectionProbeBudget() *openAISelectionProbeBudget {
	return &openAISelectionProbeBudget{attempted: make(map[int64]struct{})}
}

func (b *openAISelectionProbeBudget) enableLimit() {
	if b != nil {
		b.limited = true
	}
}

func (b *openAISelectionProbeBudget) recordAcquire(accountID int64) bool {
	if b == nil {
		return false
	}
	if !b.limited {
		return true
	}
	if b.acquires >= openAIAccountSelectionProbeLimit {
		return false
	}
	if b.attempted == nil {
		b.attempted = make(map[int64]struct{})
	}
	b.acquires++
	b.attempted[accountID] = struct{}{}
	return true
}

func (b *openAISelectionProbeBudget) recordRecheck() bool {
	if b == nil {
		return false
	}
	if !b.limited {
		return true
	}
	if b.rechecks >= openAIAccountSelectionProbeLimit {
		return false
	}
	b.rechecks++
	return true
}

func (b *openAISelectionProbeBudget) acquireExhausted() bool {
	return b != nil && b.limited && b.acquires >= openAIAccountSelectionProbeLimit
}

func (b *openAISelectionProbeBudget) wasAttempted(accountID int64) bool {
	if b == nil {
		return false
	}
	_, ok := b.attempted[accountID]
	return ok
}

type openAIStickyEscapeConfig struct {
	enabled   bool
	ttftMs    float64
	errorRate float64
}

func newDefaultOpenAIAccountScheduler(service *OpenAIGatewayService, stats *openAIAccountRuntimeStats) OpenAIAccountScheduler {
	if stats == nil {
		stats = newOpenAIAccountRuntimeStats()
	}
	return &defaultOpenAIAccountScheduler{
		service: service,
		stats:   stats,
	}
}

func (s *defaultOpenAIAccountScheduler) Select(
	ctx context.Context,
	req OpenAIAccountScheduleRequest,
) (*AccountSelectionResult, OpenAIAccountScheduleDecision, error) {
	decision := OpenAIAccountScheduleDecision{}
	start := time.Now()
	defer func() {
		decision.LatencyMs = time.Since(start).Milliseconds()
		s.metrics.recordSelect(decision)
	}()

	previousResponseID := strings.TrimSpace(req.PreviousResponseID)
	if previousResponseID != "" && NormalizeOpenAICompatiblePlatform(req.Platform) == PlatformOpenAI &&
		(!req.StickyWeighted || !req.PreviousResponseCanMove) {
		selection, err := s.service.selectAccountByPreviousResponseIDForCapability(
			ctx,
			req.GroupID,
			previousResponseID,
			req.RequestedModel,
			req.ExcludedIDs,
			req.RequiredCapability,
			req.RequireCompact,
		)
		if err != nil {
			return nil, decision, err
		}
		if selection != nil && selection.Account != nil {
			if !s.isAccountTransportCompatible(selection.Account, req.RequiredTransport) {
				if selection.ReleaseFunc != nil {
					selection.ReleaseFunc()
				}
				selection = nil
			}
		}
		if selection != nil && selection.Account != nil {
			decision.Layer = openAIAccountScheduleLayerPreviousResponse
			decision.StickyPreviousHit = true
			decision.SelectedAccountID = selection.Account.ID
			decision.SelectedAccountType = selection.Account.Type
			if req.SessionHash != "" {
				_ = s.service.bindOpenAIStickySessionDuringSelection(ctx, req.GroupID, req.SessionHash, selection.Account.ID)
			}
			return selection, decision, nil
		}
	}

	if !req.StickyWeighted {
		selection, escapedSticky, err := s.selectBySessionHash(ctx, req)
		if err != nil {
			return nil, decision, err
		}
		if selection != nil && selection.Account != nil {
			decision.Layer = openAIAccountScheduleLayerSessionSticky
			decision.StickySessionHit = true
			decision.SelectedAccountID = selection.Account.ID
			decision.SelectedAccountType = selection.Account.Type
			return selection, decision, nil
		}
		if escapedSticky {
			req.PreserveStickyBinding = true
		}
	}

	selection, candidateCount, topK, loadSkew, err := s.selectByLoadBalance(ctx, req)
	decision.Layer = openAIAccountScheduleLayerLoadBalance
	decision.CandidateCount = candidateCount
	decision.TopK = topK
	decision.LoadSkew = loadSkew
	if err != nil {
		return nil, decision, err
	}
	if selection != nil && selection.Account != nil {
		decision.SelectedAccountID = selection.Account.ID
		decision.SelectedAccountType = selection.Account.Type
		if req.StickyWeighted {
			if req.StickyPreviousAccountID > 0 && selection.Account.ID == req.StickyPreviousAccountID {
				decision.StickyPreviousHit = true
			}
			if req.StickyAccountID > 0 && selection.Account.ID == req.StickyAccountID {
				decision.StickySessionHit = true
			}
		}
	}
	return selection, decision, nil
}

func (s *defaultOpenAIAccountScheduler) selectBySessionHash(
	ctx context.Context,
	req OpenAIAccountScheduleRequest,
) (*AccountSelectionResult, bool, error) {
	sessionHash := strings.TrimSpace(req.SessionHash)
	if sessionHash == "" || s == nil || s.service == nil || s.service.cache == nil {
		return nil, false, nil
	}

	accountID := req.StickyAccountID
	if accountID <= 0 {
		var err error
		accountID, err = s.service.getStickySessionAccountID(ctx, req.GroupID, sessionHash)
		if err != nil || accountID <= 0 {
			return nil, false, nil
		}
	}
	if accountID <= 0 {
		return nil, false, nil
	}
	if req.ExcludedIDs != nil {
		if _, excluded := req.ExcludedIDs[accountID]; excluded {
			return nil, false, nil
		}
	}

	account, err := s.service.getSchedulableAccount(ctx, accountID)
	if err != nil || account == nil {
		_ = s.service.deleteStickySessionAccountID(ctx, req.GroupID, sessionHash)
		return nil, false, nil
	}
	if shouldClearStickySession(account, req.RequestedModel) || account.Platform != NormalizeOpenAICompatiblePlatform(req.Platform) || !account.IsOpenAICompatible() || !account.IsSchedulable() {
		_ = s.service.deleteStickySessionAccountID(ctx, req.GroupID, sessionHash)
		return nil, false, nil
	}
	if !s.isAccountRequestCompatible(ctx, account, req) {
		return nil, false, nil
	}
	if !s.isAccountTransportCompatible(account, req.RequiredTransport) {
		_ = s.service.deleteStickySessionAccountID(ctx, req.GroupID, sessionHash)
		return nil, false, nil
	}
	account = s.service.recheckSelectedOpenAIAccountFromDB(ctx, account, req.GroupID, req.Platform, req.RequestedModel, req.RequireCompact, req.RequiredCapability)
	if account == nil || !s.service.openAIAccountMatchesSchedulingGroup(account, req.GroupID) || !s.isAccountTransportCompatible(account, req.RequiredTransport) {
		_ = s.service.deleteStickySessionAccountID(ctx, req.GroupID, sessionHash)
		return nil, false, nil
	}
	// Free-tier soft gate: sticky session must not pin an over-quota free OAuth account.
	// Admin QueryQuota / import probes do not use this path.
	if account != nil && len(s.filterGrokFreeQuotaAccounts(ctx, []Account{*account})) == 0 {
		_ = s.service.deleteStickySessionAccountID(ctx, req.GroupID, sessionHash)
		return nil, false, nil
	}
	// Team+model cool: sticky must not pin a sibling under the same team 429 window.
	now := time.Now()
	upstreamModel := canonicalOpenAIAccountSchedulingModel(account, req.RequestedModel)
	if account != nil && isGrokTeamModelRateLimited(account, upstreamModel, now) {
		_ = s.service.deleteStickySessionAccountID(ctx, req.GroupID, sessionHash)
		return nil, false, nil
	}
	if account != nil && isGrokModelQuotaBlocked(account.ID, upstreamModel, now) {
		_ = s.service.deleteStickySessionAccountID(ctx, req.GroupID, sessionHash)
		return nil, false, nil
	}
	escapeCfg := s.service.openAIStickyEscapeConfig()
	if reason, errorRate, ttft, shouldEscape := s.shouldEscapeStickyAccount(accountID, escapeCfg); shouldEscape {
		slog.Info("sticky_escape_triggered",
			"account_id", accountID,
			"reason", reason,
			"error_rate", errorRate,
			"ttft", ttft,
		)
		return nil, true, nil
	}
	result, acquireErr := s.service.tryAcquireAccountSlot(ctx, accountID, account.Concurrency)
	if acquireErr == nil && result != nil && result.Acquired {
		_ = s.service.refreshStickySessionTTL(ctx, req.GroupID, sessionHash, s.service.openAIWSSessionStickyTTL())
		return attachSelectionProfitGate(ctx, &AccountSelectionResult{
			Account:     account,
			Acquired:    true,
			ReleaseFunc: result.ReleaseFunc,
		}), false, nil
	}

	cfg := s.service.schedulingConfig()
	// WaitPlan.MaxConcurrency 使用 Concurrency（非 EffectiveLoadFactor），因为 WaitPlan 控制的是 Redis 实际并发槽位等待。
	if s.service.concurrencyService != nil {
		if escapeCfg.enabled && acquireErr == nil && result != nil && !result.Acquired {
			errorRate, ttft, _ := s.stats.snapshot(accountID)
			slog.Info("sticky_escape_triggered",
				"account_id", accountID,
				"reason", "concurrency_full",
				"error_rate", errorRate,
				"ttft", ttft,
			)
			return nil, true, nil
		}
		return attachSelectionProfitGate(ctx, &AccountSelectionResult{
			Account: account,
			WaitPlan: &AccountWaitPlan{
				AccountID:      accountID,
				MaxConcurrency: account.Concurrency,
				Timeout:        cfg.StickySessionWaitTimeout,
				MaxWaiting:     cfg.StickySessionMaxWaiting,
			},
		}), false, nil
	}
	return nil, false, nil
}

func openAIStickyAccountMatchesGroup(account *Account, groupID *int64) bool {
	if account == nil {
		return false
	}
	if groupID == nil {
		return len(account.AccountGroups) == 0 && len(account.GroupIDs) == 0
	}
	for _, accountGroupID := range account.GroupIDs {
		if accountGroupID == *groupID {
			return true
		}
	}
	for _, accountGroup := range account.AccountGroups {
		if accountGroup.GroupID == *groupID {
			return true
		}
	}
	return false
}

func openAIAccountSchedulingPriority(account *Account) int {
	if account == nil {
		return 0
	}
	return account.Priority
}

func (s *defaultOpenAIAccountScheduler) shouldEscapeStickyAccount(accountID int64, cfg openAIStickyEscapeConfig) (reason string, errorRate float64, ttft float64, shouldEscape bool) {
	if !cfg.enabled || s == nil || s.stats == nil || accountID <= 0 {
		return "", 0, 0, false
	}
	errorRate, ttft, hasTTFT := s.stats.snapshot(accountID)
	if hasTTFT && ttft > cfg.ttftMs {
		return "ttft", errorRate, ttft, true
	}
	if errorRate > cfg.errorRate {
		return "error_rate", errorRate, ttft, true
	}
	return "", errorRate, ttft, false
}

type openAIAccountCandidateScore struct {
	account   *Account
	loadInfo  *AccountLoadInfo
	loadKnown bool
	score     float64
	priority  int
	errorRate float64
	ttft      float64
	hasTTFT   bool
}

type openAIAccountCandidateHeap []openAIAccountCandidateScore

func (h openAIAccountCandidateHeap) Len() int {
	return len(h)
}

func (h openAIAccountCandidateHeap) Less(i, j int) bool {
	// 最小堆根节点保存“最差”候选，便于 O(log k) 维护 topK。
	return isOpenAIAccountCandidateBetter(h[j], h[i])
}

func (h openAIAccountCandidateHeap) Swap(i, j int) {
	h[i], h[j] = h[j], h[i]
}

func (h *openAIAccountCandidateHeap) Push(x any) {
	candidate, ok := x.(openAIAccountCandidateScore)
	if !ok {
		panic("openAIAccountCandidateHeap: invalid element type")
	}
	*h = append(*h, candidate)
}

func (h *openAIAccountCandidateHeap) Pop() any {
	old := *h
	n := len(old)
	last := old[n-1]
	*h = old[:n-1]
	return last
}

func isOpenAIAccountCandidateBetter(left openAIAccountCandidateScore, right openAIAccountCandidateScore) bool {
	if left.score != right.score {
		return left.score > right.score
	}
	if left.account.Priority != right.account.Priority {
		return left.account.Priority < right.account.Priority
	}
	if left.loadInfo.LoadRate != right.loadInfo.LoadRate {
		return left.loadInfo.LoadRate < right.loadInfo.LoadRate
	}
	if left.loadInfo.WaitingCount != right.loadInfo.WaitingCount {
		return left.loadInfo.WaitingCount < right.loadInfo.WaitingCount
	}
	return left.account.ID < right.account.ID
}

func selectTopKOpenAICandidates(candidates []openAIAccountCandidateScore, topK int) []openAIAccountCandidateScore {
	if len(candidates) == 0 {
		return nil
	}
	if topK <= 0 {
		topK = 1
	}
	if topK >= len(candidates) {
		ranked := append([]openAIAccountCandidateScore(nil), candidates...)
		sort.Slice(ranked, func(i, j int) bool {
			return isOpenAIAccountCandidateBetter(ranked[i], ranked[j])
		})
		return ranked
	}

	best := make(openAIAccountCandidateHeap, 0, topK)
	for _, candidate := range candidates {
		if len(best) < topK {
			heap.Push(&best, candidate)
			continue
		}
		if isOpenAIAccountCandidateBetter(candidate, best[0]) {
			best[0] = candidate
			heap.Fix(&best, 0)
		}
	}

	ranked := make([]openAIAccountCandidateScore, len(best))
	copy(ranked, best)
	sort.Slice(ranked, func(i, j int) bool {
		return isOpenAIAccountCandidateBetter(ranked[i], ranked[j])
	})
	return ranked
}

type openAISelectionRNG struct {
	state uint64
}

func newOpenAISelectionRNG(seed uint64) openAISelectionRNG {
	if seed == 0 {
		seed = 0x9e3779b97f4a7c15
	}
	return openAISelectionRNG{state: seed}
}

func (r *openAISelectionRNG) nextUint64() uint64 {
	// xorshift64*
	x := r.state
	x ^= x >> 12
	x ^= x << 25
	x ^= x >> 27
	r.state = x
	return x * 2685821657736338717
}

func (r *openAISelectionRNG) nextFloat64() float64 {
	// [0,1)
	return float64(r.nextUint64()>>11) / (1 << 53)
}

func deriveOpenAISelectionSeed(req OpenAIAccountScheduleRequest) uint64 {
	hasher := fnv.New64a()
	writeValue := func(value string) {
		trimmed := strings.TrimSpace(value)
		if trimmed == "" {
			return
		}
		_, _ = hasher.Write([]byte(trimmed))
		_, _ = hasher.Write([]byte{0})
	}

	writeValue(req.SessionHash)
	writeValue(req.PreviousResponseID)
	writeValue(req.RequestedModel)
	if req.GroupID != nil {
		_, _ = hasher.Write([]byte(strconv.FormatInt(*req.GroupID, 10)))
	}

	seed := hasher.Sum64()
	// 对“无会话锚点”的纯负载均衡请求引入时间熵，避免固定命中同一账号。
	if strings.TrimSpace(req.SessionHash) == "" && strings.TrimSpace(req.PreviousResponseID) == "" {
		seed ^= uint64(time.Now().UnixNano())
	}
	if seed == 0 {
		seed = uint64(time.Now().UnixNano()) ^ 0x9e3779b97f4a7c15
	}
	return seed
}

func buildOpenAIWeightedSelectionOrder(
	candidates []openAIAccountCandidateScore,
	req OpenAIAccountScheduleRequest,
) []openAIAccountCandidateScore {
	if len(candidates) <= 1 {
		return append([]openAIAccountCandidateScore(nil), candidates...)
	}

	pool := append([]openAIAccountCandidateScore(nil), candidates...)
	weights := make([]float64, len(pool))
	minScore := pool[0].score
	for i := 1; i < len(pool); i++ {
		if pool[i].score < minScore {
			minScore = pool[i].score
		}
	}
	for i := range pool {
		// 将 top-K 分值平移到正区间，避免“单一最高分账号”长期垄断。
		weight := (pool[i].score - minScore) + 1.0
		if math.IsNaN(weight) || math.IsInf(weight, 0) || weight <= 0 {
			weight = 1.0
		}
		weights[i] = weight
	}

	order := make([]openAIAccountCandidateScore, 0, len(pool))
	rng := newOpenAISelectionRNG(deriveOpenAISelectionSeed(req))
	for len(pool) > 0 {
		total := 0.0
		for _, w := range weights {
			total += w
		}

		selectedIdx := 0
		if total > 0 {
			r := rng.nextFloat64() * total
			acc := 0.0
			for i, w := range weights {
				acc += w
				if r <= acc {
					selectedIdx = i
					break
				}
			}
		} else {
			selectedIdx = int(rng.nextUint64() % uint64(len(pool)))
		}

		order = append(order, pool[selectedIdx])
		pool = append(pool[:selectedIdx], pool[selectedIdx+1:]...)
		weights = append(weights[:selectedIdx], weights[selectedIdx+1:]...)
	}
	return order
}

func (s *defaultOpenAIAccountScheduler) buildOpenAIAccountLoadPlan(
	ctx context.Context,
	req OpenAIAccountScheduleRequest,
	filtered []*Account,
	loadMap map[int64]*AccountLoadInfo,
) openAIAccountLoadPlan {
	allCandidates := make([]openAIAccountCandidateScore, 0, len(filtered))
	for _, account := range filtered {
		loadInfo, loadKnown := loadMap[account.ID]
		if !loadKnown || loadInfo == nil {
			loadInfo = &AccountLoadInfo{AccountID: account.ID}
			loadKnown = false
		}
		errorRate, ttft, hasTTFT := 0.0, 0.0, false
		if s.stats != nil {
			errorRate, ttft, hasTTFT = s.stats.snapshot(account.ID)
		}
		allCandidates = append(allCandidates, openAIAccountCandidateScore{
			account:   account,
			loadInfo:  loadInfo,
			loadKnown: loadKnown,
			errorRate: errorRate,
			ttft:      ttft,
			hasTTFT:   hasTTFT,
		})
	}

	candidates := allCandidates
	staleSnapshotCompactRetry := make([]openAIAccountCandidateScore, 0, len(allCandidates))
	if req.RequireCompact {
		candidates = make([]openAIAccountCandidateScore, 0, len(allCandidates))
		for _, candidate := range allCandidates {
			if openAICompactSupportTier(candidate.account) == 0 {
				staleSnapshotCompactRetry = append(staleSnapshotCompactRetry, candidate)
				continue
			}
			candidates = append(candidates, candidate)
		}
	}

	plan := openAIAccountLoadPlan{
		allCandidates:             allCandidates,
		candidates:                candidates,
		staleSnapshotCompactRetry: staleSnapshotCompactRetry,
		candidateCount:            len(candidates),
	}
	if len(candidates) == 0 {
		plan.selectionOrder = s.buildOpenAISelectionOrder(req, plan)
		return plan
	}

	minPriority, maxPriority := openAIAccountSchedulingPriority(candidates[0].account), openAIAccountSchedulingPriority(candidates[0].account)
	maxWaiting := 1
	loadRateSum := 0.0
	loadRateSumSquares := 0.0
	minTTFT, maxTTFT := 0.0, 0.0
	hasTTFTSample := false
	for i := range candidates {
		candidate := &candidates[i]
		candidate.priority = openAIAccountSchedulingPriority(candidate.account)
		if candidate.priority < minPriority {
			minPriority = candidate.priority
		}
		if candidate.priority > maxPriority {
			maxPriority = candidate.priority
		}
		if candidate.loadInfo.WaitingCount > maxWaiting {
			maxWaiting = candidate.loadInfo.WaitingCount
		}
		if candidate.hasTTFT && candidate.ttft > 0 {
			if !hasTTFTSample {
				minTTFT, maxTTFT = candidate.ttft, candidate.ttft
				hasTTFTSample = true
			} else {
				if candidate.ttft < minTTFT {
					minTTFT = candidate.ttft
				}
				if candidate.ttft > maxTTFT {
					maxTTFT = candidate.ttft
				}
			}
		}
		loadRate := float64(candidate.loadInfo.LoadRate)
		loadRateSum += loadRate
		loadRateSumSquares += loadRate * loadRate
	}
	plan.loadSkew = calcLoadSkewByMoments(loadRateSum, loadRateSumSquares, len(candidates))

	weights := s.service.openAIWSSchedulerWeightsForRequest(ctx)
	now := time.Now()
	upstreamCostFactors := map[int64]float64(nil)
	if req.UseUpstreamTokenCost && weights.UpstreamCost > 0 {
		accounts := make([]*Account, 0, len(candidates))
		for _, candidate := range candidates {
			accounts = append(accounts, candidate.account)
		}
		upstreamCostFactors = openAIUpstreamCostFactors(accounts, now, s.service.openAIOAuthSchedulingRateMultiplier(ctx))
		for _, factor := range upstreamCostFactors {
			if factor != openAIUpstreamCostNeutralFactor {
				plan.includeOverflowFallback = true
				break
			}
		}
	}

	// Reset 因子（use-it-or-lose-it）：在拥有「未来会话窗口结束时间」的账号中，
	// 剩余时间越短 → 因子越接近 1（越早重置越优先用尽）。无活跃窗口的账号因子为 0。
	// 仅在 weights.Reset > 0 时计算，默认关闭不影响原有行为。
	minResetRemaining, maxResetRemaining := 0.0, 0.0
	hasResetSample := false
	if weights.Reset > 0 {
		for _, candidate := range candidates {
			end := candidate.account.SessionWindowEnd
			if end == nil || !now.Before(*end) {
				continue
			}
			remaining := end.Sub(now).Seconds()
			if !hasResetSample {
				minResetRemaining, maxResetRemaining = remaining, remaining
				hasResetSample = true
				continue
			}
			if remaining < minResetRemaining {
				minResetRemaining = remaining
			}
			if remaining > maxResetRemaining {
				maxResetRemaining = remaining
			}
		}
	}

	for i := range candidates {
		item := &candidates[i]
		priorityFactor := 1.0
		if maxPriority > minPriority {
			priorityFactor = 1 - float64(item.priority-minPriority)/float64(maxPriority-minPriority)
		}
		loadFactor := 1 - clamp01(float64(item.loadInfo.LoadRate)/100.0)
		queueFactor := 1 - clamp01(float64(item.loadInfo.WaitingCount)/float64(maxWaiting))
		errorFactor := 1 - clamp01(item.errorRate)
		ttftFactor := 0.5
		if item.hasTTFT && hasTTFTSample && maxTTFT > minTTFT {
			ttftFactor = 1 - clamp01((item.ttft-minTTFT)/(maxTTFT-minTTFT))
		}
		resetFactor := 0.0
		if weights.Reset > 0 && hasResetSample {
			if end := item.account.SessionWindowEnd; end != nil && now.Before(*end) {
				if maxResetRemaining > minResetRemaining {
					resetFactor = 1 - clamp01((end.Sub(now).Seconds()-minResetRemaining)/(maxResetRemaining-minResetRemaining))
				} else {
					// 所有有窗口的账号剩余时间相同：一律给满分，让其优于无窗口账号。
					resetFactor = 1
				}
			}
		}
		quotaHeadroomFactor := 0.0
		if weights.QuotaHeadroom > 0 {
			quotaHeadroomFactor = openAIQuotaHeadroomFactor(item.account, now)
		}
		upstreamCostFactor := openAIUpstreamCostNeutralFactor
		if factor, ok := upstreamCostFactors[item.account.ID]; ok {
			upstreamCostFactor = factor
		}

		item.score = weights.Priority*priorityFactor +
			weights.Load*loadFactor +
			weights.Queue*queueFactor +
			weights.ErrorRate*errorFactor +
			weights.TTFT*ttftFactor +
			weights.Reset*resetFactor +
			weights.QuotaHeadroom*quotaHeadroomFactor +
			weights.UpstreamCost*(upstreamCostFactor-openAIUpstreamCostNeutralFactor)
		if req.StickyWeighted {
			if req.PreviousResponseCanMove && req.StickyPreviousAccountID > 0 && item.account.ID == req.StickyPreviousAccountID {
				item.score += weights.Previous
			}
			if req.StickyAccountID > 0 && item.account.ID == req.StickyAccountID {
				item.score += weights.SessionSticky
			}
		}
	}
	plan.candidates = candidates

	plan.topK = s.service.openAIWSLBTopKForRequest(ctx)
	if plan.topK > len(candidates) {
		plan.topK = len(candidates)
	}
	if plan.topK <= 0 {
		plan.topK = 1
	}

	plan.selectionOrder = s.buildOpenAISelectionOrder(req, plan)
	return plan
}

func (s *defaultOpenAIAccountScheduler) buildOpenAISelectionOrder(
	req OpenAIAccountScheduleRequest,
	plan openAIAccountLoadPlan,
) []openAIAccountCandidateScore {
	buildSelectionOrder := func(pool []openAIAccountCandidateScore) []openAIAccountCandidateScore {
		if len(pool) == 0 || plan.topK <= 0 {
			return nil
		}
		groupTopK := plan.topK
		if groupTopK > len(pool) {
			groupTopK = len(pool)
		}
		ranked := selectTopKOpenAICandidates(pool, groupTopK)
		var primary []openAIAccountCandidateScore
		if req.StickyWeighted {
			for _, stickyID := range []int64{req.StickyPreviousAccountID, req.StickyAccountID} {
				if stickyID <= 0 {
					continue
				}
				for i, candidate := range ranked {
					if candidate.account != nil && candidate.account.ID == stickyID {
						primary = append([]openAIAccountCandidateScore{candidate}, ranked[:i]...)
						primary = append(primary, ranked[i+1:]...)
						break
					}
				}
				if len(primary) > 0 {
					break
				}
			}
		}
		if len(primary) == 0 {
			primary = buildOpenAIWeightedSelectionOrder(ranked, req)
		}
		if !plan.includeOverflowFallback || groupTopK >= len(pool) {
			return primary
		}

		selected := make(map[int64]struct{}, len(primary))
		for _, candidate := range primary {
			selected[candidate.account.ID] = struct{}{}
		}
		overflow := make([]openAIAccountCandidateScore, 0, len(pool)-len(primary))
		for _, candidate := range pool {
			if _, ok := selected[candidate.account.ID]; !ok {
				overflow = append(overflow, candidate)
			}
		}
		sort.Slice(overflow, func(i, j int) bool {
			return isOpenAIAccountCandidateBetter(overflow[i], overflow[j])
		})
		return append(primary, overflow...)
	}

	if req.RequireCompact {
		supported := make([]openAIAccountCandidateScore, 0, len(plan.candidates))
		unknown := make([]openAIAccountCandidateScore, 0, len(plan.candidates))
		for _, candidate := range plan.candidates {
			switch openAICompactSupportTier(candidate.account) {
			case 2:
				supported = append(supported, candidate)
			case 1:
				unknown = append(unknown, candidate)
			}
		}
		selectionOrder := make([]openAIAccountCandidateScore, 0, len(plan.allCandidates))
		selectionOrder = append(selectionOrder, buildSelectionOrder(supported)...)
		selectionOrder = append(selectionOrder, buildSelectionOrder(unknown)...)
		if len(plan.staleSnapshotCompactRetry) > 0 && s.service.schedulerSnapshot != nil {
			selectionOrder = append(selectionOrder, sortOpenAICompactRetryCandidates(plan.staleSnapshotCompactRetry)...)
		}
		return selectionOrder
	}

	return buildSelectionOrder(plan.candidates)
}

func sortOpenAICompactRetryCandidates(pool []openAIAccountCandidateScore) []openAIAccountCandidateScore {
	if len(pool) == 0 {
		return nil
	}
	ordered := append([]openAIAccountCandidateScore(nil), pool...)
	sort.SliceStable(ordered, func(i, j int) bool {
		a, b := ordered[i], ordered[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
		}
		if a.loadInfo.WaitingCount != b.loadInfo.WaitingCount {
			return a.loadInfo.WaitingCount < b.loadInfo.WaitingCount
		}
		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)
		}
	})
	return ordered
}

func (s *defaultOpenAIAccountScheduler) tryAcquireOpenAISelectionOrder(
	ctx context.Context,
	req OpenAIAccountScheduleRequest,
	selectionOrder []openAIAccountCandidateScore,
) (*AccountSelectionResult, bool, error) {
	budget := newOpenAISelectionProbeBudget()
	budget.enableLimit()
	return s.tryAcquireOpenAISelectionOrderWithBudget(ctx, req, selectionOrder, budget)
}

func (s *defaultOpenAIAccountScheduler) tryAcquireOpenAISelectionOrderWithBudget(
	ctx context.Context,
	req OpenAIAccountScheduleRequest,
	selectionOrder []openAIAccountCandidateScore,
	budget *openAISelectionProbeBudget,
) (*AccountSelectionResult, bool, error) {
	compactBlocked := false
	release := func(result *AcquireResult) {
		if result != nil && result.ReleaseFunc != nil {
			result.ReleaseFunc()
		}
	}
	for i := 0; i < len(selectionOrder); i++ {
		candidate := selectionOrder[i]
		if candidate.account == nil {
			continue
		}
		if candidate.loadKnown && candidate.account.Concurrency > 0 &&
			candidate.loadInfo.CurrentConcurrency >= candidate.account.Concurrency {
			continue
		}

		result, attempted, acquireErr := s.tryAcquireOpenAIAccountSlot(ctx, candidate.account.ID, candidate.account.Concurrency, budget)
		if !attempted {
			break
		}
		if acquireErr != nil {
			return nil, compactBlocked, acquireErr
		}
		if result == nil || !result.Acquired {
			continue
		}

		fresh := s.service.resolveFreshSchedulableOpenAIAccount(ctx, candidate.account, req.Platform, req.RequestedModel, false, req.RequiredCapability)
		if fresh == nil || !s.isAccountTransportCompatible(fresh, req.RequiredTransport) || !s.isAccountRequestCompatible(ctx, fresh, req) {
			release(result)
			continue
		}
		if !s.consumeOpenAISelectionDBRecheck(budget) {
			release(result)
			break
		}
		fresh = s.service.recheckSelectedOpenAIAccountFromDB(ctx, fresh, req.GroupID, req.Platform, req.RequestedModel, false, req.RequiredCapability)
		if fresh == nil || !s.isAccountTransportCompatible(fresh, req.RequiredTransport) || !s.isAccountRequestCompatible(ctx, fresh, req) {
			release(result)
			continue
		}
		if req.RequireCompact && openAICompactSupportTier(fresh) == 0 {
			compactBlocked = true
			release(result)
			continue
		}

		if fresh.Concurrency != candidate.account.Concurrency {
			release(result)
			result, attempted, acquireErr = s.tryAcquireOpenAIAccountSlot(ctx, fresh.ID, fresh.Concurrency, budget)
			if !attempted {
				continue
			}
			if acquireErr != nil {
				return nil, compactBlocked, acquireErr
			}
			if result == nil || !result.Acquired {
				continue
			}
		}
		if req.SessionHash != "" && !req.PreserveStickyBinding {
			_ = s.service.bindOpenAIStickySessionDuringSelection(ctx, req.GroupID, req.SessionHash, fresh.ID)
		}
		return attachSelectionProfitGate(ctx, &AccountSelectionResult{
			Account:     fresh,
			Acquired:    true,
			ReleaseFunc: result.ReleaseFunc,
		}), compactBlocked, nil
	}
	return nil, compactBlocked, nil
}

func (s *defaultOpenAIAccountScheduler) tryAcquireOpenAIAccountSlot(
	ctx context.Context,
	accountID int64,
	maxConcurrency int,
	budget *openAISelectionProbeBudget,
) (*AcquireResult, bool, error) {
	if s.service.concurrencyService != nil && maxConcurrency > 0 && !budget.recordAcquire(accountID) {
		return nil, false, nil
	}
	result, err := s.service.tryAcquireAccountSlot(ctx, accountID, maxConcurrency)
	return result, true, err
}

func (s *defaultOpenAIAccountScheduler) consumeOpenAISelectionDBRecheck(budget *openAISelectionProbeBudget) bool {
	if s.service.schedulerSnapshot == nil || s.service.accountRepo == nil {
		return true
	}
	return budget.recordRecheck()
}

func (s *defaultOpenAIAccountScheduler) tryFallbackToWeightedSticky(
	ctx context.Context,
	req OpenAIAccountScheduleRequest,
) (*AccountSelectionResult, error) {
	if !req.StickyWeighted {
		return nil, nil
	}
	for _, accountID := range []int64{req.StickyPreviousAccountID, req.StickyAccountID} {
		if accountID <= 0 {
			continue
		}
		if req.ExcludedIDs != nil {
			if _, excluded := req.ExcludedIDs[accountID]; excluded {
				continue
			}
		}
		account, err := s.service.getSchedulableAccount(ctx, accountID)
		if err != nil || account == nil {
			continue
		}
		if !s.isAccountRequestCompatible(ctx, account, req) || !s.isAccountTransportCompatible(account, req.RequiredTransport) {
			continue
		}
		account = s.service.recheckSelectedOpenAIAccountFromDB(ctx, account, req.GroupID, req.Platform, req.RequestedModel, req.RequireCompact, req.RequiredCapability)
		if account == nil {
			if accountID == req.StickyAccountID && strings.TrimSpace(req.SessionHash) != "" {
				_ = s.service.deleteStickySessionAccountID(ctx, req.GroupID, req.SessionHash)
			}
			continue
		}
		if !s.service.openAIAccountMatchesSchedulingGroup(account, req.GroupID) {
			if accountID == req.StickyAccountID && strings.TrimSpace(req.SessionHash) != "" {
				_ = s.service.deleteStickySessionAccountID(ctx, req.GroupID, req.SessionHash)
			}
			continue
		}
		if !s.isAccountRequestCompatible(ctx, account, req) || !s.isAccountTransportCompatible(account, req.RequiredTransport) {
			continue
		}
		if req.RequireCompact && openAICompactSupportTier(account) == 0 {
			continue
		}
		// Keep weighted sticky fallback subject to the same free-tier gate as the
		// normal and sticky selection paths. Otherwise an over-quota free account
		// could be reintroduced after the primary candidate pass.
		if len(s.filterGrokFreeQuotaAccounts(ctx, []Account{*account})) == 0 {
			continue
		}
		upstreamModel := canonicalOpenAIAccountSchedulingModel(account, req.RequestedModel)
		now := time.Now()
		if isGrokTeamModelRateLimited(account, upstreamModel, now) ||
			isGrokModelQuotaBlocked(account.ID, upstreamModel, now) {
			continue
		}
		result, acquireErr := s.service.tryAcquireAccountSlot(ctx, account.ID, account.Concurrency)
		if acquireErr != nil {
			return nil, acquireErr
		}
		if result != nil && result.Acquired {
			if req.SessionHash != "" && !req.PreserveStickyBinding {
				_ = s.service.bindOpenAIStickySessionDuringSelection(ctx, req.GroupID, req.SessionHash, account.ID)
			}
			return attachSelectionProfitGate(ctx, &AccountSelectionResult{
				Account:     account,
				Acquired:    true,
				ReleaseFunc: result.ReleaseFunc,
			}), nil
		}
		if s.service.concurrencyService != nil {
			cfg := s.service.schedulingConfig()
			return attachSelectionProfitGate(ctx, &AccountSelectionResult{
				Account: account,
				WaitPlan: &AccountWaitPlan{
					AccountID:      account.ID,
					MaxConcurrency: account.Concurrency,
					Timeout:        cfg.StickySessionWaitTimeout,
					MaxWaiting:     cfg.StickySessionMaxWaiting,
				},
			}), nil
		}
	}
	return nil, nil
}

// openAISelectionFilterStats counts why candidates were dropped by the
// selectByLoadBalance initial filter. Historically these exclusions were
// silent (debug logs at best), so a "no available accounts" failure with
// excluded_account_count=0 was undiagnosable from the error alone (#4599).
// The reasons map is lazily allocated: on the happy path (nothing filtered
// out, or an account is eventually selected) no extra allocation happens.
type openAISelectionFilterStats struct {
	pool    int
	reasons map[string]int
}

func (s *openAISelectionFilterStats) exclude(reason string) {
	if s.reasons == nil {
		s.reasons = make(map[string]int, 4)
	}
	s.reasons[reason]++
}

// summary renders deterministic exclusion statistics for scheduling error
// messages, e.g. "pool=3, filtered: model_not_supported=2 quota_auto_pause_7d=1".
// Reasons are sorted lexicographically so the output is stable for tests and
// log aggregation. extra, when non-empty, is appended as a trailing marker.
func (s openAISelectionFilterStats) summary(extra string) string {
	var b strings.Builder
	_, _ = b.WriteString("pool=")
	_, _ = b.WriteString(strconv.Itoa(s.pool))
	if len(s.reasons) > 0 {
		reasons := make([]string, 0, len(s.reasons))
		for reason := range s.reasons {
			reasons = append(reasons, reason)
		}
		sort.Strings(reasons)
		_, _ = b.WriteString(", filtered:")
		for _, reason := range reasons {
			_, _ = b.WriteString(" ")
			_, _ = b.WriteString(reason)
			_, _ = b.WriteString("=")
			_, _ = b.WriteString(strconv.Itoa(s.reasons[reason]))
		}
	}
	if extra != "" {
		_, _ = b.WriteString(", ")
		_, _ = b.WriteString(extra)
	}
	return b.String()
}

func (s *defaultOpenAIAccountScheduler) selectByLoadBalance(
	ctx context.Context,
	req OpenAIAccountScheduleRequest,
) (*AccountSelectionResult, int, int, float64, error) {
	budget := newOpenAISelectionProbeBudget()
	accounts, err := s.service.listSchedulableAccounts(ctx, req.GroupID, req.Platform)
	if err != nil {
		return nil, 0, 0, 0, err
	}
	if len(accounts) == 0 {
		return nil, 0, 0, 0, noAvailableOpenAISelectionError(req.RequestedModel, false, openAISelectionFilterStats{}.summary(""))
	}
	// Local free-tier soft gate on the Grok scheduling path only (not admin probe).
	accounts = s.filterGrokFreeQuotaAccounts(ctx, accounts)
	if len(accounts) == 0 {
		return nil, 0, 0, 0, noAvailableOpenAISelectionError(req.RequestedModel, false, openAISelectionFilterStats{}.summary("grok_free_quota_soft_gate"))
	}
	// Team+model rate-limit cool: siblings of a 429'd team skip the hot model.
	if req.Platform == PlatformGrok {
		now := time.Now()
		filtered := filterGrokTeamModelRateLimitedAccounts(accounts, req.RequestedModel, now)
		if len(filtered) == 0 && len(accounts) > 0 {
			return nil, 0, 0, 0, noAvailableOpenAISelectionError(req.RequestedModel, false, openAISelectionFilterStats{}.summary("grok_team_model_rate_limit"))
		}
		if filtered != nil {
			accounts = filtered
		}
		// Per-account model free-usage soft-block (other models stay eligible).
		modelFiltered := filterGrokModelQuotaBlockedAccounts(accounts, req.RequestedModel, now)
		if len(modelFiltered) == 0 && len(accounts) > 0 {
			return nil, 0, 0, 0, noAvailableOpenAISelectionError(req.RequestedModel, false, openAISelectionFilterStats{}.summary("grok_model_quota_block"))
		}
		accounts = modelFiltered
	}

	// require_privacy_set: 获取分组信息
	var schedGroup *Group
	if req.GroupID != nil && s.service.schedulerSnapshot != nil {
		schedGroup, _ = s.service.schedulerSnapshot.GetGroupByID(ctx, *req.GroupID)
	}

	filterStats := openAISelectionFilterStats{pool: len(accounts)}
	filtered := make([]*Account, 0, len(accounts))
	loadReq := make([]AccountWithConcurrency, 0, len(accounts))
	for i := range accounts {
		account := &accounts[i]
		if req.ExcludedIDs != nil {
			if _, excluded := req.ExcludedIDs[account.ID]; excluded {
				filterStats.exclude("excluded")
				continue
			}
		}
		if !account.IsSchedulable() {
			filterStats.exclude("not_schedulable")
			continue
		}
		if account.Platform != NormalizeOpenAICompatiblePlatform(req.Platform) || !account.IsOpenAICompatible() {
			filterStats.exclude("platform_mismatch")
			continue
		}
		if s.service.isOpenAIAccountRequestRuntimeBlocked(account, req.RequestedModel) {
			filterStats.exclude("runtime_blocked")
			continue
		}
		// require_privacy_set: 跳过 privacy 未设置的账号并标记异常
		if schedGroup != nil && schedGroup.RequirePrivacySet && !account.IsPrivacySet() {
			s.service.BlockAccountScheduling(account, time.Time{}, "privacy_not_set")
			_ = s.service.accountRepo.SetError(ctx, account.ID,
				fmt.Sprintf("Privacy not set, required by group [%s]", schedGroup.Name))
			filterStats.exclude("privacy_not_set")
			continue
		}
		if compatible, reason := s.isAccountRequestCompatibleReason(ctx, account, req); !compatible {
			filterStats.exclude(reason)
			continue
		}
		if !s.isAccountTransportCompatible(account, req.RequiredTransport) {
			filterStats.exclude("transport_incompatible")
			continue
		}
		filtered = append(filtered, account)
		loadReq = append(loadReq, AccountWithConcurrency{
			ID:             account.ID,
			MaxConcurrency: account.EffectiveLoadFactor(),
		})
	}
	if len(filtered) == 0 {
		return nil, 0, 0, 0, noAvailableOpenAISelectionError(req.RequestedModel, false, filterStats.summary(""))
	}

	loadMap := map[int64]*AccountLoadInfo{}
	if s.service.concurrencyService != nil {
		if batchLoad, loadErr := s.service.concurrencyService.GetAccountsLoadBatch(ctx, loadReq); loadErr == nil {
			loadMap = batchLoad
		}
	}

	if req.SubscriptionPriority {
		subscriptionAccounts, regularAccounts := partitionOpenAIChatGPTSubscriptionAccounts(filtered)
		if len(subscriptionAccounts) > 0 {
			attempt := s.trySelectByLoadBalancePool(ctx, req, subscriptionAccounts, loadMap, budget)
			if attempt.err != nil && (!attempt.noCompactCandidates || len(regularAccounts) <= 0) {
				return nil, attempt.candidateCount, attempt.topK, attempt.loadSkew, attempt.err
			}
			if attempt.result != nil {
				return attempt.result, attempt.candidateCount, attempt.topK, attempt.loadSkew, nil
			}
			if len(regularAccounts) > 0 {
				regularAttempt := s.trySelectByLoadBalancePool(ctx, req, regularAccounts, loadMap, budget)
				if regularAttempt.err != nil && !regularAttempt.noCompactCandidates {
					return nil, regularAttempt.candidateCount, regularAttempt.topK, regularAttempt.loadSkew, regularAttempt.err
				}
				if regularAttempt.result != nil {
					return regularAttempt.result, regularAttempt.candidateCount, regularAttempt.topK, regularAttempt.loadSkew, nil
				}
				var result *AccountSelectionResult
				candidateCount, topK, loadSkew := regularAttempt.candidateCount, regularAttempt.topK, regularAttempt.loadSkew
				fallbackErr := regularAttempt.err
				if regularAttempt.err == nil {
					result, candidateCount, topK, loadSkew, fallbackErr = s.finishLoadBalanceSelectionFallback(ctx, req, regularAttempt, budget, filterStats)
					if fallbackErr == nil && result != nil {
						return result, candidateCount, topK, loadSkew, nil
					}
				}
				// 常规池既无法获取也无法排队（含仅剩不支持 compact 的候选）时，
				// 回退到订阅池的等待计划：busy-but-waitable 的订阅账号不应因常规池存在
				// 而被丢弃，否则开启订阅优先反而让本可排队成功的请求硬失败。
				subResult, subCandidateCount, subTopK, subLoadSkew, subErr := s.finishLoadBalanceSelectionFallback(ctx, req, attempt, budget, filterStats)
				if subErr == nil && subResult != nil {
					return subResult, subCandidateCount, subTopK, subLoadSkew, nil
				}
				return result, candidateCount, topK, loadSkew, fallbackErr
			}
			return s.finishLoadBalanceSelectionFallback(ctx, req, attempt, budget, filterStats)
		}
	}

	attempt := s.trySelectByLoadBalancePool(ctx, req, filtered, loadMap, budget)
	if attempt.err != nil {
		return nil, attempt.candidateCount, attempt.topK, attempt.loadSkew, attempt.err
	}
	if attempt.result != nil {
		return attempt.result, attempt.candidateCount, attempt.topK, attempt.loadSkew, nil
	}
	return s.finishLoadBalanceSelectionFallback(ctx, req, attempt, budget, filterStats)
}

func partitionOpenAIChatGPTSubscriptionAccounts(accounts []*Account) ([]*Account, []*Account) {
	subscriptionAccounts := make([]*Account, 0, len(accounts))
	regularAccounts := make([]*Account, 0, len(accounts))
	for _, account := range accounts {
		if account != nil && account.IsOpenAIChatGPTSubscription() {
			subscriptionAccounts = append(subscriptionAccounts, account)
			continue
		}
		regularAccounts = append(regularAccounts, account)
	}
	return subscriptionAccounts, regularAccounts
}

func (s *defaultOpenAIAccountScheduler) trySelectByLoadBalancePool(
	ctx context.Context,
	req OpenAIAccountScheduleRequest,
	filtered []*Account,
	loadMap map[int64]*AccountLoadInfo,
	budget *openAISelectionProbeBudget,
) openAIAccountLoadSelectionAttempt {
	plan := s.buildOpenAIAccountLoadPlan(ctx, req, filtered, loadMap)
	if openAICostOverflowExpanded(req, plan) {
		budget.enableLimit()
	}
	attempt := openAIAccountLoadSelectionAttempt{
		selectionOrder: plan.selectionOrder,
		candidateCount: plan.candidateCount,
		topK:           plan.topK,
		loadSkew:       plan.loadSkew,
	}
	if req.RequireCompact && len(plan.candidates) == 0 && len(plan.staleSnapshotCompactRetry) == 0 {
		attempt.noCompactCandidates = true
		attempt.err = ErrNoAvailableCompactAccounts
		return attempt
	}
	if req.RequireCompact && len(attempt.selectionOrder) == 0 && s.service.schedulerSnapshot == nil {
		attempt.noCompactCandidates = true
		attempt.err = ErrNoAvailableCompactAccounts
		return attempt
	}
	if len(attempt.selectionOrder) == 0 {
		attempt.compactBlocked = req.RequireCompact && len(plan.allCandidates) > 0
		return attempt
	}

	result, compactBlocked, acquireErr := s.tryAcquireOpenAISelectionOrderWithBudget(ctx, req, attempt.selectionOrder, budget)
	attempt.compactBlocked = compactBlocked
	if acquireErr != nil {
		attempt.err = acquireErr
		return attempt
	}
	if result != nil {
		attempt.result = result
		return attempt
	}

	if s.service.concurrencyService != nil && !budget.acquireExhausted() {
		loadReq := buildOpenAIAccountLoadRequest(filtered)
		if freshLoadMap, loadErr := s.service.concurrencyService.GetAccountsLoadBatchFresh(ctx, loadReq); loadErr == nil {
			freshPlan := s.buildOpenAIAccountLoadPlan(ctx, req, filtered, freshLoadMap)
			if openAICostOverflowExpanded(req, freshPlan) {
				budget.enableLimit()
			}
			if len(freshPlan.selectionOrder) > 0 {
				freshResult, freshCompactBlocked, freshAcquireErr := s.tryAcquireOpenAISelectionOrderWithBudget(ctx, req, freshPlan.selectionOrder, budget)
				if freshAcquireErr != nil {
					attempt.err = freshAcquireErr
					return attempt
				}
				if freshResult != nil {
					attempt.result = freshResult
					attempt.selectionOrder = freshPlan.selectionOrder
					attempt.candidateCount = freshPlan.candidateCount
					attempt.topK = freshPlan.topK
					attempt.loadSkew = freshPlan.loadSkew
					return attempt
				}
				attempt.compactBlocked = attempt.compactBlocked || freshCompactBlocked
				attempt.selectionOrder = freshPlan.selectionOrder
				attempt.candidateCount = freshPlan.candidateCount
				attempt.topK = freshPlan.topK
				attempt.loadSkew = freshPlan.loadSkew
			}
		}
	}

	return attempt
}

func openAICostOverflowExpanded(req OpenAIAccountScheduleRequest, plan openAIAccountLoadPlan) bool {
	if !plan.includeOverflowFallback || plan.topK <= 0 {
		return false
	}
	if !req.RequireCompact {
		return len(plan.candidates) > plan.topK
	}
	supported, unknown := 0, 0
	for _, candidate := range plan.candidates {
		switch openAICompactSupportTier(candidate.account) {
		case 2:
			supported++
		case 1:
			unknown++
		}
	}
	return supported > plan.topK || unknown > plan.topK
}

func buildOpenAIAccountLoadRequest(accounts []*Account) []AccountWithConcurrency {
	loadReq := make([]AccountWithConcurrency, 0, len(accounts))
	for _, account := range accounts {
		if account == nil {
			continue
		}
		loadReq = append(loadReq, AccountWithConcurrency{
			ID:             account.ID,
			MaxConcurrency: account.EffectiveLoadFactor(),
		})
	}
	return loadReq
}

func (s *defaultOpenAIAccountScheduler) finishLoadBalanceSelectionFallback(
	ctx context.Context,
	req OpenAIAccountScheduleRequest,
	attempt openAIAccountLoadSelectionAttempt,
	budget *openAISelectionProbeBudget,
	filterStats openAISelectionFilterStats,
) (*AccountSelectionResult, int, int, float64, error) {
	candidateCount := attempt.candidateCount
	topK := attempt.topK
	loadSkew := attempt.loadSkew

	if len(attempt.selectionOrder) == 0 {
		return nil, candidateCount, topK, loadSkew, noAvailableOpenAISelectionError(req.RequestedModel, attempt.compactBlocked, filterStats.summary("selection_order_empty"))
	}

	if stickyFallback, stickyErr := s.tryFallbackToWeightedSticky(ctx, req); stickyErr != nil {
		return nil, candidateCount, topK, loadSkew, stickyErr
	} else if stickyFallback != nil {
		return stickyFallback, candidateCount, topK, loadSkew, nil
	}

	cfg := s.service.schedulingConfig()
	compactBlocked := attempt.compactBlocked
	// WaitPlan.MaxConcurrency 使用 Concurrency（非 EffectiveLoadFactor），因为 WaitPlan 控制的是 Redis 实际并发槽位等待。
	passes := 1
	if budget != nil && budget.limited {
		passes = 4
	}
	for pass := 0; pass < passes; pass++ {
		wantAttempted := pass == 1 || pass == 3
		wantKnownFull := pass >= 2
		for _, candidate := range attempt.selectionOrder {
			if candidate.account == nil {
				continue
			}
			if budget != nil && budget.limited {
				knownFull := candidate.loadKnown && candidate.account.Concurrency > 0 &&
					candidate.loadInfo.CurrentConcurrency >= candidate.account.Concurrency
				if budget.wasAttempted(candidate.account.ID) != wantAttempted || knownFull != wantKnownFull {
					continue
				}
			}
			fresh := s.service.resolveFreshSchedulableOpenAIAccount(ctx, candidate.account, req.Platform, req.RequestedModel, false, req.RequiredCapability)
			if fresh == nil || !s.isAccountTransportCompatible(fresh, req.RequiredTransport) || !s.isAccountRequestCompatible(ctx, fresh, req) {
				continue
			}
			if !s.consumeOpenAISelectionDBRecheck(budget) {
				return nil, candidateCount, topK, loadSkew, noAvailableOpenAISelectionError(req.RequestedModel, compactBlocked, filterStats.summary("selection_order_exhausted"))
			}
			fresh = s.service.recheckSelectedOpenAIAccountFromDB(ctx, fresh, req.GroupID, req.Platform, req.RequestedModel, false, req.RequiredCapability)
			if fresh == nil || !s.isAccountTransportCompatible(fresh, req.RequiredTransport) || !s.isAccountRequestCompatible(ctx, fresh, req) {
				continue
			}
			if req.RequireCompact && openAICompactSupportTier(fresh) == 0 {
				compactBlocked = true
				continue
			}
			return attachSelectionProfitGate(ctx, &AccountSelectionResult{
				Account: fresh,
				WaitPlan: &AccountWaitPlan{
					AccountID:      fresh.ID,
					MaxConcurrency: fresh.Concurrency,
					Timeout:        cfg.FallbackWaitTimeout,
					MaxWaiting:     cfg.FallbackMaxWaiting,
				},
			}), candidateCount, topK, loadSkew, nil
		}
	}

	return nil, candidateCount, topK, loadSkew, noAvailableOpenAISelectionError(req.RequestedModel, compactBlocked, filterStats.summary("selection_order_exhausted"))
}

func (s *defaultOpenAIAccountScheduler) isAccountTransportCompatible(account *Account, requiredTransport OpenAIUpstreamTransport) bool {
	if requiredTransport == OpenAIUpstreamTransportAny || requiredTransport == OpenAIUpstreamTransportHTTPSSE {
		return true
	}
	if s == nil || s.service == nil {
		return false
	}
	return s.service.isOpenAIAccountTransportCompatible(account, requiredTransport)
}

func (s *defaultOpenAIAccountScheduler) lookupShadowParentAccount(ctx context.Context, id int64) *Account {
	if s == nil || s.service == nil {
		return nil
	}
	if s.service.schedulerSnapshot != nil {
		if account, err := s.service.schedulerSnapshot.GetAccount(ctx, id); err == nil && account != nil {
			return account
		}
	}
	if s.service.accountRepo == nil {
		return nil
	}
	account, _ := s.service.accountRepo.GetByID(ctx, id)
	return account
}

func (s *defaultOpenAIAccountScheduler) isAccountRequestCompatible(ctx context.Context, account *Account, req OpenAIAccountScheduleRequest) bool {
	compatible, _ := s.isAccountRequestCompatibleReason(ctx, account, req)
	return compatible
}

// isAccountRequestCompatibleReason reports whether the account can serve the
// request, and when it cannot, names the veto point. The reason feeds
// openAISelectionFilterStats so that "no available accounts" errors state why
// each candidate was dropped instead of failing silently (#4599).
func (s *defaultOpenAIAccountScheduler) isAccountRequestCompatibleReason(ctx context.Context, account *Account, req OpenAIAccountScheduleRequest) (bool, string) {
	if account == nil {
		return false, "account_nil"
	}
	if s != nil && s.service != nil && s.service.isOpenAIAccountRequestRuntimeBlocked(account, req.RequestedModel) {
		return false, "runtime_blocked"
	}
	if s != nil && s.service != nil && s.service.isOpenAIProxyStreamQuarantined(ctx, account) {
		return false, "proxy_stream_quarantined"
	}
	// Quota auto-pause must be evaluated during the initial filter too. Without it the
	// TopK candidate pool can be filled with paused accounts and the later fresh/DB
	// rechecks won't reach healthy accounts that fell outside TopK — manifesting as
	// "no available accounts" even though healthy ones exist.
	if paused, decision := shouldAutoPauseOpenAIAccountByQuota(ctx, account); paused {
		reason := "quota_auto_pause"
		if decision.window != "" {
			reason += "_" + decision.window
		}
		return false, reason
	}
	// 母账号健康联动：影子账号的凭据来自母账号，母账号不可调度时影子也不应被选中。
	// Parent-health gate: shadow borrows the parent's credentials; an unschedulable
	// parent must block the shadow across all scheduler paths.
	if !parentHealthyForShadow(account, func(id int64) *Account {
		return s.lookupShadowParentAccount(ctx, id)
	}) {
		return false, "shadow_parent_unhealthy"
	}
	if req.RequestedModel != "" && !account.IsModelSupported(req.RequestedModel) {
		return false, "model_not_supported"
	}
	if req.GroupID != nil && s != nil && s.service != nil &&
		s.service.needsUpstreamChannelRestrictionCheck(ctx, req.GroupID) &&
		s.service.isUpstreamModelRestrictedByChannel(ctx, *req.GroupID, account, req.RequestedModel, req.RequireCompact) {
		return false, "channel_upstream_restricted"
	}
	if !accountSupportsOpenAICapabilities(account, req.RequiredCapability, req.RequiredImageCapability) {
		return false, "capability_mismatch"
	}
	// 分组利润控制：不合格账号在候选过滤与抢槽后终检阶段即被排除，
	// 排序/评分/粘性/熔断只在合格账号之间工作；named reason 进入 filter stats。
	if vetoed, reason := openAIProfitControlVetoReason(ctx, account); vetoed {
		return false, reason
	}
	return true, ""
}

func (s *defaultOpenAIAccountScheduler) ReportResult(accountID int64, success bool, firstTokenMs *int) {
	if s == nil || s.stats == nil {
		return
	}
	s.stats.report(accountID, success, firstTokenMs)
}

func (s *defaultOpenAIAccountScheduler) ReportSwitch() {
	if s == nil {
		return
	}
	s.metrics.recordSwitch()
}

func (s *defaultOpenAIAccountScheduler) SnapshotMetrics() OpenAIAccountSchedulerMetricsSnapshot {
	if s == nil {
		return OpenAIAccountSchedulerMetricsSnapshot{}
	}

	selectTotal := s.metrics.selectTotal.Load()
	prevHit := s.metrics.stickyPreviousHitTotal.Load()
	sessionHit := s.metrics.stickySessionHitTotal.Load()
	switchTotal := s.metrics.accountSwitchTotal.Load()
	latencyTotal := s.metrics.latencyMsTotal.Load()
	loadSkewTotal := s.metrics.loadSkewMilliTotal.Load()

	snapshot := OpenAIAccountSchedulerMetricsSnapshot{
		SelectTotal:              selectTotal,
		StickyPreviousHitTotal:   prevHit,
		StickySessionHitTotal:    sessionHit,
		LoadBalanceSelectTotal:   s.metrics.loadBalanceSelectTotal.Load(),
		AccountSwitchTotal:       switchTotal,
		SchedulerLatencyMsTotal:  latencyTotal,
		RuntimeStatsAccountCount: s.stats.size(),
	}
	if selectTotal > 0 {
		snapshot.SchedulerLatencyMsAvg = float64(latencyTotal) / float64(selectTotal)
		snapshot.StickyHitRatio = float64(prevHit+sessionHit) / float64(selectTotal)
		snapshot.AccountSwitchRate = float64(switchTotal) / float64(selectTotal)
		snapshot.LoadSkewAvg = float64(loadSkewTotal) / 1000 / float64(selectTotal)
	}
	return snapshot
}

func (s *OpenAIGatewayService) openAIAdvancedSchedulerSettingRepo() SettingRepository {
	if s == nil || s.rateLimitService == nil || s.rateLimitService.settingService == nil {
		return nil
	}
	return s.rateLimitService.settingService.settingRepo
}

func (s *OpenAIGatewayService) openAIAdvancedSchedulerRuntimeSettings(ctx context.Context) openAIAdvancedSchedulerRuntimeSettings {
	if cached, ok := openAIAdvancedSchedulerSettingCache.Load().(*cachedOpenAIAdvancedSchedulerSetting); ok && cached != nil {
		if time.Now().UnixNano() < cached.expiresAt {
			return openAIAdvancedSchedulerRuntimeSettings{
				lowUpstreamRatePriorityEnabled: cached.lowUpstreamRatePriorityEnabled,
				oauthSchedulingRateMultiplier:  cached.oauthSchedulingRateMultiplier,
				enabled:                        cached.enabled,
				stickyWeightedEnabled:          cached.stickyWeightedEnabled,
				subscriptionPriorityEnabled:    cached.subscriptionPriorityEnabled,
				lbTopKOverride:                 cached.lbTopKOverride,
				weightOverrides:                cloneOpenAIAdvancedSchedulerWeightOverrides(cached.weightOverrides),
			}
		}
	}

	result, _, _ := openAIAdvancedSchedulerSettingSF.Do(openAIAdvancedSchedulerSettingKey, func() (any, error) {
		if cached, ok := openAIAdvancedSchedulerSettingCache.Load().(*cachedOpenAIAdvancedSchedulerSetting); ok && cached != nil {
			if time.Now().UnixNano() < cached.expiresAt {
				return openAIAdvancedSchedulerRuntimeSettings{
					lowUpstreamRatePriorityEnabled: cached.lowUpstreamRatePriorityEnabled,
					oauthSchedulingRateMultiplier:  cached.oauthSchedulingRateMultiplier,
					enabled:                        cached.enabled,
					stickyWeightedEnabled:          cached.stickyWeightedEnabled,
					subscriptionPriorityEnabled:    cached.subscriptionPriorityEnabled,
					lbTopKOverride:                 cached.lbTopKOverride,
					weightOverrides:                cloneOpenAIAdvancedSchedulerWeightOverrides(cached.weightOverrides),
				}, nil
			}
		}

		lowUpstreamRatePriorityEnabled := false
		oauthSchedulingRateMultiplier := defaultOpenAIOAuthSchedulingRateMultiplier
		enabled := false
		stickyWeightedEnabled := false
		subscriptionPriorityEnabled := false
		lbTopKOverride := 0
		weightOverrides := map[string]float64{}
		if repo := s.openAIAdvancedSchedulerSettingRepo(); repo != nil {
			dbCtx, cancel := context.WithTimeout(context.WithoutCancel(ctx), openAIAdvancedSchedulerSettingDBTimeout)
			defer cancel()

			if values, err := repo.GetMultiple(dbCtx, openAIAdvancedSchedulerRuntimeSettingKeys()); err == nil {
				lowUpstreamRatePriorityEnabled = strings.EqualFold(strings.TrimSpace(values[SettingKeyOpenAILowUpstreamRatePriorityEnabled]), "true")
				oauthSchedulingRateMultiplier = parseOpenAIOAuthSchedulingRateMultiplier(values[SettingKeyOpenAIOAuthSchedulingRateMultiplier])
				enabled = strings.EqualFold(strings.TrimSpace(values[openAIAdvancedSchedulerSettingKey]), "true")
				stickyWeightedEnabled = strings.EqualFold(strings.TrimSpace(values[SettingKeyOpenAIAdvancedSchedulerStickyWeightedEnabled]), "true")
				subscriptionPriorityEnabled = strings.EqualFold(strings.TrimSpace(values[SettingKeyOpenAIAdvancedSchedulerSubscriptionPriorityEnabled]), "true")
				lbTopKOverride = parsePositiveIntOverride(values[SettingKeyOpenAIAdvancedSchedulerLBTopK])
				weightOverrides = parseOpenAIAdvancedSchedulerWeightOverrides(values)
			} else {
				// 批量读取失败时逐键降级，覆盖全部键（含 TopK/权重），避免只加载布尔开关
				// 而静默丢弃管理员配置的覆盖值；降级状态会被缓存一个 TTL，必须留痕。
				slog.Warn("openai_advanced_scheduler_settings_batch_load_failed", "error", err)
				fallbackValues := make(map[string]string)
				for _, key := range openAIAdvancedSchedulerRuntimeSettingKeys() {
					if value, valueErr := repo.GetValue(dbCtx, key); valueErr == nil {
						fallbackValues[key] = value
					}
				}
				lowUpstreamRatePriorityEnabled = strings.EqualFold(strings.TrimSpace(fallbackValues[SettingKeyOpenAILowUpstreamRatePriorityEnabled]), "true")
				oauthSchedulingRateMultiplier = parseOpenAIOAuthSchedulingRateMultiplier(fallbackValues[SettingKeyOpenAIOAuthSchedulingRateMultiplier])
				enabled = strings.EqualFold(strings.TrimSpace(fallbackValues[openAIAdvancedSchedulerSettingKey]), "true")
				stickyWeightedEnabled = strings.EqualFold(strings.TrimSpace(fallbackValues[SettingKeyOpenAIAdvancedSchedulerStickyWeightedEnabled]), "true")
				subscriptionPriorityEnabled = strings.EqualFold(strings.TrimSpace(fallbackValues[SettingKeyOpenAIAdvancedSchedulerSubscriptionPriorityEnabled]), "true")
				lbTopKOverride = parsePositiveIntOverride(fallbackValues[SettingKeyOpenAIAdvancedSchedulerLBTopK])
				weightOverrides = parseOpenAIAdvancedSchedulerWeightOverrides(fallbackValues)
			}
		}

		openAIAdvancedSchedulerSettingCache.Store(&cachedOpenAIAdvancedSchedulerSetting{
			lowUpstreamRatePriorityEnabled: lowUpstreamRatePriorityEnabled,
			oauthSchedulingRateMultiplier:  oauthSchedulingRateMultiplier,
			enabled:                        enabled,
			stickyWeightedEnabled:          stickyWeightedEnabled,
			subscriptionPriorityEnabled:    subscriptionPriorityEnabled,
			lbTopKOverride:                 lbTopKOverride,
			weightOverrides:                cloneOpenAIAdvancedSchedulerWeightOverrides(weightOverrides),
			expiresAt:                      time.Now().Add(openAIAdvancedSchedulerSettingCacheTTL).UnixNano(),
		})
		return openAIAdvancedSchedulerRuntimeSettings{
			lowUpstreamRatePriorityEnabled: lowUpstreamRatePriorityEnabled,
			oauthSchedulingRateMultiplier:  oauthSchedulingRateMultiplier,
			enabled:                        enabled,
			stickyWeightedEnabled:          stickyWeightedEnabled,
			subscriptionPriorityEnabled:    subscriptionPriorityEnabled,
			lbTopKOverride:                 lbTopKOverride,
			weightOverrides:                weightOverrides,
		}, nil
	})

	settings, _ := result.(openAIAdvancedSchedulerRuntimeSettings)
	return settings
}

func (s *OpenAIGatewayService) isOpenAIAdvancedSchedulerEnabled(ctx context.Context) bool {
	return s.openAIAdvancedSchedulerRuntimeSettings(ctx).enabled
}

func (s *OpenAIGatewayService) isOpenAILowUpstreamRatePriorityEnabled(ctx context.Context) bool {
	settings := s.openAIAdvancedSchedulerRuntimeSettings(ctx)
	return !settings.enabled && settings.lowUpstreamRatePriorityEnabled
}

func (s *OpenAIGatewayService) openAIOAuthSchedulingRateMultiplier(ctx context.Context) float64 {
	return s.openAIAdvancedSchedulerRuntimeSettings(ctx).oauthSchedulingRateMultiplier
}

func (s *OpenAIGatewayService) isOpenAIAdvancedSchedulerStickyWeightedEnabled(ctx context.Context) bool {
	settings := s.openAIAdvancedSchedulerRuntimeSettings(ctx)
	return settings.enabled && settings.stickyWeightedEnabled
}

func (s *OpenAIGatewayService) isOpenAIAdvancedSchedulerSubscriptionPriorityEnabled(ctx context.Context) bool {
	settings := s.openAIAdvancedSchedulerRuntimeSettings(ctx)
	return settings.enabled && settings.subscriptionPriorityEnabled
}

func openAIAdvancedSchedulerRuntimeSettingKeys() []string {
	keys := []string{
		SettingKeyOpenAILowUpstreamRatePriorityEnabled,
		SettingKeyOpenAIOAuthSchedulingRateMultiplier,
		openAIAdvancedSchedulerSettingKey,
		SettingKeyOpenAIAdvancedSchedulerStickyWeightedEnabled,
		SettingKeyOpenAIAdvancedSchedulerSubscriptionPriorityEnabled,
		SettingKeyOpenAIAdvancedSchedulerLBTopK,
	}
	for _, spec := range openAIAdvancedSchedulerWeightOverrideSpecs() {
		keys = append(keys, spec.key)
	}
	return keys
}

type openAIAdvancedSchedulerWeightOverrideSpec struct {
	key  string
	name string
}

func openAIAdvancedSchedulerWeightOverrideSpecs() []openAIAdvancedSchedulerWeightOverrideSpec {
	return []openAIAdvancedSchedulerWeightOverrideSpec{
		{key: SettingKeyOpenAIAdvancedSchedulerWeightPriority, name: "priority"},
		{key: SettingKeyOpenAIAdvancedSchedulerWeightLoad, name: "load"},
		{key: SettingKeyOpenAIAdvancedSchedulerWeightQueue, name: "queue"},
		{key: SettingKeyOpenAIAdvancedSchedulerWeightErrorRate, name: "error_rate"},
		{key: SettingKeyOpenAIAdvancedSchedulerWeightTTFT, name: "ttft"},
		{key: SettingKeyOpenAIAdvancedSchedulerWeightReset, name: "reset"},
		{key: SettingKeyOpenAIAdvancedSchedulerWeightQuotaHeadroom, name: "quota_headroom"},
		{key: SettingKeyOpenAIAdvancedSchedulerWeightUpstreamCost, name: "upstream_cost"},
		{key: SettingKeyOpenAIAdvancedSchedulerWeightPreviousResponse, name: "previous_response"},
		{key: SettingKeyOpenAIAdvancedSchedulerWeightSessionSticky, name: "session_sticky"},
	}
}

func parsePositiveIntOverride(raw string) int {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return 0
	}
	value, err := strconv.Atoi(raw)
	if err != nil || value <= 0 {
		return 0
	}
	return value
}

func parseOpenAIAdvancedSchedulerWeightOverrides(values map[string]string) map[string]float64 {
	overrides := map[string]float64{}
	for _, spec := range openAIAdvancedSchedulerWeightOverrideSpecs() {
		raw := strings.TrimSpace(values[spec.key])
		if raw == "" {
			continue
		}
		value, err := strconv.ParseFloat(raw, 64)
		if err != nil || value < 0 || math.IsNaN(value) || math.IsInf(value, 0) {
			continue
		}
		overrides[spec.name] = value
	}
	return overrides
}

func cloneOpenAIAdvancedSchedulerWeightOverrides(in map[string]float64) map[string]float64 {
	if len(in) == 0 {
		return nil
	}
	out := make(map[string]float64, len(in))
	for key, value := range in {
		out[key] = value
	}
	return out
}

func (s *OpenAIGatewayService) getOpenAIAccountScheduler(ctx context.Context) OpenAIAccountScheduler {
	if s == nil {
		return nil
	}
	if !s.isOpenAIAdvancedSchedulerEnabled(ctx) {
		return nil
	}
	s.openaiSchedulerOnce.Do(func() {
		if s.openaiAccountStats == nil {
			s.openaiAccountStats = newOpenAIAccountRuntimeStats()
		}
		if s.openaiScheduler == nil {
			s.openaiScheduler = newDefaultOpenAIAccountScheduler(s, s.openaiAccountStats)
		}
	})
	return s.openaiScheduler
}

func resetOpenAIAdvancedSchedulerSettingCacheForTest() {
	openAIAdvancedSchedulerSettingCache = atomic.Value{}
	openAIAdvancedSchedulerSettingSF = singleflight.Group{}
}

func (s *OpenAIGatewayService) SelectAccountWithScheduler(
	ctx context.Context,
	groupID *int64,
	previousResponseID string,
	sessionHash string,
	requestedModel string,
	excludedIDs map[int64]struct{},
	requiredTransport OpenAIUpstreamTransport,
	requireCompact bool,
) (*AccountSelectionResult, OpenAIAccountScheduleDecision, error) {
	return s.selectAccountWithScheduler(ctx, groupID, previousResponseID, sessionHash, requestedModel, excludedIDs, requiredTransport, "", "", requireCompact, PlatformOpenAI, false, true)
}

// SelectAccountWithSchedulerForCapability 按能力要求调度账号。
// previousResponseCanMove 表示首包 input 可自行重建工具续链，previous_response_id 允许跨账号迁移
// （粘性加权模式下改为加权偏好而非硬粘连）。
func (s *OpenAIGatewayService) SelectAccountWithSchedulerForCapability(
	ctx context.Context,
	groupID *int64,
	previousResponseID string,
	sessionHash string,
	requestedModel string,
	excludedIDs map[int64]struct{},
	requiredTransport OpenAIUpstreamTransport,
	requiredCapability OpenAIEndpointCapability,
	requireCompact bool,
	previousResponseCanMove bool,
	useUpstreamTokenCost bool,
	platformOverride ...string,
) (*AccountSelectionResult, OpenAIAccountScheduleDecision, error) {
	platform := PlatformOpenAI
	if len(platformOverride) > 0 {
		platform = platformOverride[0]
	}
	return s.selectAccountWithScheduler(ctx, groupID, previousResponseID, sessionHash, requestedModel, excludedIDs, requiredTransport, requiredCapability, "", requireCompact, platform, previousResponseCanMove, useUpstreamTokenCost)
}

func (s *OpenAIGatewayService) SelectAccountWithSchedulerForImages(
	ctx context.Context,
	groupID *int64,
	sessionHash string,
	requestedModel string,
	excludedIDs map[int64]struct{},
	requiredCapability OpenAIImagesCapability,
) (*AccountSelectionResult, OpenAIAccountScheduleDecision, error) {
	selection, decision, err := s.selectAccountWithScheduler(ctx, groupID, "", sessionHash, requestedModel, excludedIDs, OpenAIUpstreamTransportHTTPSSE, "", requiredCapability, false, PlatformOpenAI, false, false)
	if err == nil && selection != nil && selection.Account != nil {
		return selection, decision, nil
	}
	// 如果要求 native 能力（如指定了模型）但没有可用的 APIKey 账号，回退到 basic（OAuth 账号）
	if requiredCapability == OpenAIImagesCapabilityNative {
		return s.selectAccountWithScheduler(ctx, groupID, "", sessionHash, requestedModel, excludedIDs, OpenAIUpstreamTransportHTTPSSE, "", OpenAIImagesCapabilityBasic, false, PlatformOpenAI, false, false)
	}
	return selection, decision, err
}

// selectAccountWithScheduler wraps selectAccountWithSchedulerOnce with a
// fail-open second pass for the proxy stream circuit (#5056): when the only
// reason no account is available is that every candidate sits behind a
// quarantined proxy, the quarantine must degrade to a preference instead of
// zeroing out capacity. The retry re-runs the exact same selection with the
// quarantine checks bypassed, so healthy proxies always win the first pass
// and quarantined ones only serve when nothing else can.
func (s *OpenAIGatewayService) selectAccountWithScheduler(
	ctx context.Context,
	groupID *int64,
	previousResponseID string,
	sessionHash string,
	requestedModel string,
	excludedIDs map[int64]struct{},
	requiredTransport OpenAIUpstreamTransport,
	requiredCapability OpenAIEndpointCapability,
	requiredImageCapability OpenAIImagesCapability,
	requireCompact bool,
	platform string,
	previousResponseCanMove bool,
	useUpstreamTokenCost bool,
) (*AccountSelectionResult, OpenAIAccountScheduleDecision, error) {
	selection, decision, err := s.selectAccountWithSchedulerOnce(ctx, groupID, previousResponseID, sessionHash, requestedModel, excludedIDs, requiredTransport, requiredCapability, requiredImageCapability, requireCompact, platform, previousResponseCanMove, useUpstreamTokenCost)
	if err == nil || openAIProxyStreamQuarantineBypassed(ctx) {
		return selection, decision, err
	}
	if !errors.Is(err, ErrNoAvailableAccounts) && !errors.Is(err, ErrNoAvailableCompactAccounts) {
		return selection, decision, err
	}
	// The circuit only ever quarantines PlatformOpenAI accounts.
	if NormalizeOpenAICompatiblePlatform(platform) != PlatformOpenAI {
		return selection, decision, err
	}
	blocked := s.getOpenAIProxyStreamCircuit().activeBlockCount(time.Now())
	if blocked == 0 {
		return selection, decision, err
	}
	s.logOpenAIProxyStreamQuarantineFailOpen(requestedModel, blocked)
	return s.selectAccountWithSchedulerOnce(withOpenAIProxyStreamQuarantineBypass(ctx), groupID, previousResponseID, sessionHash, requestedModel, excludedIDs, requiredTransport, requiredCapability, requiredImageCapability, requireCompact, platform, previousResponseCanMove, useUpstreamTokenCost)
}

func (s *OpenAIGatewayService) selectAccountWithSchedulerOnce(
	ctx context.Context,
	groupID *int64,
	previousResponseID string,
	sessionHash string,
	requestedModel string,
	excludedIDs map[int64]struct{},
	requiredTransport OpenAIUpstreamTransport,
	requiredCapability OpenAIEndpointCapability,
	requiredImageCapability OpenAIImagesCapability,
	requireCompact bool,
	platform string,
	previousResponseCanMove bool,
	useUpstreamTokenCost bool,
) (*AccountSelectionResult, OpenAIAccountScheduleDecision, error) {
	ctx = s.withOpenAIQuotaAutoPauseContext(ctx)
	// 分组利润控制：唯一文本调度入口的防御性装门。handler 文本
	// 入口已在请求开始经 WithOpenAIRequestPricingContext 装门并固定 pricingAt，
	// 此处对同分组门直接复用（failover 重入阈值稳定），仅为不经 handler 装配的
	// 内部调用兜底。图片/视频调度不在利润门范围：requiredImageCapability 非空的
	// Images 调度不装门；其他使用 Responses 能力的文本请求（包括原生远程压缩）
	// 仍须装门。其余媒体路径通过 WithOpenAIProfitControlSuppressed 显式跳过。
	if requiredImageCapability == "" {
		ctx = s.withOpenAIProfitControlGate(ctx, groupID)
	}
	platform = NormalizeOpenAICompatiblePlatform(platform)
	decision := OpenAIAccountScheduleDecision{}
	scheduler := s.getOpenAIAccountScheduler(ctx)
	if scheduler == nil {
		decision.Layer = openAIAccountScheduleLayerLoadBalance
		if requiredTransport == OpenAIUpstreamTransportAny || requiredTransport == OpenAIUpstreamTransportHTTPSSE {
			effectiveExcludedIDs := cloneExcludedAccountIDs(excludedIDs)
			for {
				selection, err := s.selectAccountWithLoadAwareness(ctx, groupID, platform, sessionHash, requestedModel, effectiveExcludedIDs, requireCompact, requiredCapability, useUpstreamTokenCost)
				if err != nil {
					return nil, decision, err
				}
				if selection == nil || selection.Account == nil {
					return selection, decision, nil
				}
				if accountSupportsOpenAICapabilities(selection.Account, requiredCapability, requiredImageCapability) {
					return selection, decision, nil
				}
				if selection.ReleaseFunc != nil {
					selection.ReleaseFunc()
				}
				if effectiveExcludedIDs == nil {
					effectiveExcludedIDs = make(map[int64]struct{})
				}
				if _, exists := effectiveExcludedIDs[selection.Account.ID]; exists {
					return nil, decision, ErrNoAvailableAccounts
				}
				effectiveExcludedIDs[selection.Account.ID] = struct{}{}
			}
		}

		effectiveExcludedIDs := cloneExcludedAccountIDs(excludedIDs)
		for {
			selection, err := s.selectAccountWithLoadAwareness(ctx, groupID, platform, sessionHash, requestedModel, effectiveExcludedIDs, requireCompact, requiredCapability, useUpstreamTokenCost)
			if err != nil {
				return nil, decision, err
			}
			if selection == nil || selection.Account == nil {
				return selection, decision, nil
			}
			if s.isOpenAIAccountTransportCompatible(selection.Account, requiredTransport) &&
				accountSupportsOpenAICapabilities(selection.Account, requiredCapability, requiredImageCapability) {
				return selection, decision, nil
			}
			if selection.ReleaseFunc != nil {
				selection.ReleaseFunc()
			}
			if effectiveExcludedIDs == nil {
				effectiveExcludedIDs = make(map[int64]struct{})
			}
			if _, exists := effectiveExcludedIDs[selection.Account.ID]; exists {
				return nil, decision, ErrNoAvailableAccounts
			}
			effectiveExcludedIDs[selection.Account.ID] = struct{}{}
		}
	}

	if s.checkChannelPricingRestriction(ctx, groupID, requestedModel) {
		slog.Warn("channel pricing restriction blocked request",
			"group_id", derefGroupID(groupID),
			"model", requestedModel)
		return nil, decision, fmt.Errorf("%w supporting model: %s (channel pricing restriction)", ErrNoAvailableAccounts, requestedModel)
	}

	var stickyAccountID int64
	if sessionHash != "" && s.cache != nil {
		if accountID, err := s.getStickySessionAccountID(ctx, groupID, sessionHash); err == nil && accountID > 0 {
			stickyAccountID = accountID
		}
	}
	stickyWeighted := s.isOpenAIAdvancedSchedulerStickyWeightedEnabled(ctx)
	subscriptionPriority := s.isOpenAIAdvancedSchedulerSubscriptionPriorityEnabled(ctx)
	stickyPreviousAccountID := int64(0)
	if stickyWeighted && previousResponseCanMove && strings.TrimSpace(previousResponseID) != "" && platform == PlatformOpenAI {
		stickyPreviousAccountID = s.ResolveAccountIDByPreviousResponseIDForScheduler(ctx, groupID, previousResponseID, requestedModel, excludedIDs, requiredCapability, requireCompact)
	}

	return scheduler.Select(ctx, OpenAIAccountScheduleRequest{
		GroupID:                 groupID,
		Platform:                platform,
		SessionHash:             sessionHash,
		StickyAccountID:         stickyAccountID,
		StickyPreviousAccountID: stickyPreviousAccountID,
		StickyWeighted:          stickyWeighted,
		SubscriptionPriority:    subscriptionPriority,
		PreviousResponseID:      previousResponseID,
		PreviousResponseCanMove: previousResponseCanMove,
		UseUpstreamTokenCost:    useUpstreamTokenCost,
		RequestedModel:          requestedModel,
		RequiredTransport:       requiredTransport,
		RequiredCapability:      requiredCapability,
		RequiredImageCapability: requiredImageCapability,
		RequireCompact:          requireCompact,
		ExcludedIDs:             excludedIDs,
	})
}

func accountSupportsOpenAICapabilities(account *Account, requiredCapability OpenAIEndpointCapability, requiredImageCapability OpenAIImagesCapability) bool {
	if account == nil {
		return false
	}
	return account.SupportsOpenAIEndpointCapability(requiredCapability) &&
		account.SupportsOpenAIImageCapability(requiredImageCapability)
}

func cloneExcludedAccountIDs(excludedIDs map[int64]struct{}) map[int64]struct{} {
	if len(excludedIDs) == 0 {
		return nil
	}
	cloned := make(map[int64]struct{}, len(excludedIDs))
	for id := range excludedIDs {
		cloned[id] = struct{}{}
	}
	return cloned
}

func (s *OpenAIGatewayService) isOpenAIAccountTransportCompatible(account *Account, requiredTransport OpenAIUpstreamTransport) bool {
	if requiredTransport == OpenAIUpstreamTransportAny || requiredTransport == OpenAIUpstreamTransportHTTPSSE {
		return true
	}
	if s == nil || account == nil {
		return false
	}
	if requiredTransport == OpenAIUpstreamTransportResponsesWebsocketV2Ingress {
		if s.cfg == nil || !s.cfg.Gateway.OpenAIWS.ModeRouterV2Enabled {
			return s.getOpenAIWSProtocolResolver().Resolve(account).Transport == OpenAIUpstreamTransportResponsesWebsocketV2
		}
		mode := account.ResolveOpenAIResponsesWebSocketV2Mode(s.cfg.Gateway.OpenAIWS.IngressModeDefault)
		switch mode {
		case OpenAIWSIngressModeCtxPool, OpenAIWSIngressModePassthrough, OpenAIWSIngressModeHTTPBridge, OpenAIWSIngressModeShared, OpenAIWSIngressModeDedicated:
			return true
		default:
			return false
		}
	}
	return s.getOpenAIWSProtocolResolver().Resolve(account).Transport == requiredTransport
}

func (s *OpenAIGatewayService) ReportOpenAIAccountScheduleResult(accountID int64, model string, success bool, firstTokenMs *int) {
	if success {
		s.clearOpenAIAccountModelTransientState(accountID, normalizeOpenAIAccountModelTransientModel(model))
	}
	scheduler := s.getOpenAIAccountScheduler(context.Background())
	if scheduler == nil {
		return
	}
	scheduler.ReportResult(accountID, success, firstTokenMs)
}

func (s *OpenAIGatewayService) RecordOpenAIAccountSwitch() {
	scheduler := s.getOpenAIAccountScheduler(context.Background())
	if scheduler == nil {
		return
	}
	scheduler.ReportSwitch()
}

func (s *OpenAIGatewayService) SnapshotOpenAIAccountSchedulerMetrics() OpenAIAccountSchedulerMetricsSnapshot {
	scheduler := s.getOpenAIAccountScheduler(context.Background())
	if scheduler == nil {
		return OpenAIAccountSchedulerMetricsSnapshot{}
	}
	return scheduler.SnapshotMetrics()
}

func (s *OpenAIGatewayService) openAIWSSessionStickyTTL() time.Duration {
	if s != nil && s.cfg != nil && s.cfg.Gateway.OpenAIWS.StickySessionTTLSeconds > 0 {
		return time.Duration(s.cfg.Gateway.OpenAIWS.StickySessionTTLSeconds) * time.Second
	}
	return openaiStickySessionTTL
}

func (s *OpenAIGatewayService) openAIWSLBTopK() int {
	if s != nil && s.cfg != nil && s.cfg.Gateway.OpenAIWS.LBTopK > 0 {
		return s.cfg.Gateway.OpenAIWS.LBTopK
	}
	return 7
}

func (s *OpenAIGatewayService) openAIWSLBTopKForRequest(ctx context.Context) int {
	base := s.openAIWSLBTopK()
	settings := s.openAIAdvancedSchedulerRuntimeSettings(ctx)
	// DB 覆盖值与 stickyWeighted/subscriptionPriority 一样受总开关门控：
	// 关闭高级调度器后所有调用方（含管理页分数快照）都应回到配置/默认行为。
	if !settings.enabled {
		return base
	}
	if settings.lbTopKOverride > 0 {
		return settings.lbTopKOverride
	}
	return base
}

func (s *OpenAIGatewayService) openAIStickyEscapeConfig() openAIStickyEscapeConfig {
	if s != nil && s.cfg != nil {
		cfg := s.cfg.Gateway.OpenAIScheduler
		enabled := cfg.StickyEscapeEnabled
		if !enabled && cfg.StickyEscapeTTFTMs == 0 && cfg.StickyEscapeErrorRate == 0 {
			enabled = true
		}
		ttftMs := float64(cfg.StickyEscapeTTFTMs)
		if ttftMs <= 0 {
			ttftMs = 15000
		}
		errorRate := cfg.StickyEscapeErrorRate
		if errorRate < 0 || errorRate > 1 {
			errorRate = 0.5
		}
		if errorRate == 0 && cfg.StickyEscapeTTFTMs == 0 && cfg.StickyEscapeErrorRate == 0 {
			errorRate = 0.5
		}
		return openAIStickyEscapeConfig{
			enabled:   enabled,
			ttftMs:    ttftMs,
			errorRate: errorRate,
		}
	}
	return openAIStickyEscapeConfig{
		enabled:   true,
		ttftMs:    15000,
		errorRate: 0.5,
	}
}

func (s *OpenAIGatewayService) openAIWSSchedulerWeights() GatewayOpenAIWSSchedulerScoreWeightsView {
	if s != nil && s.cfg != nil {
		return GatewayOpenAIWSSchedulerScoreWeightsView{
			Priority:      s.cfg.Gateway.OpenAIWS.SchedulerScoreWeights.Priority,
			Load:          s.cfg.Gateway.OpenAIWS.SchedulerScoreWeights.Load,
			Queue:         s.cfg.Gateway.OpenAIWS.SchedulerScoreWeights.Queue,
			ErrorRate:     s.cfg.Gateway.OpenAIWS.SchedulerScoreWeights.ErrorRate,
			TTFT:          s.cfg.Gateway.OpenAIWS.SchedulerScoreWeights.TTFT,
			Reset:         s.cfg.Gateway.OpenAIWS.SchedulerScoreWeights.Reset,
			QuotaHeadroom: s.cfg.Gateway.OpenAIWS.SchedulerScoreWeights.QuotaHeadroom,
			UpstreamCost:  s.cfg.Gateway.OpenAIWS.SchedulerScoreWeights.UpstreamCost,
			Previous:      s.cfg.Gateway.OpenAIWS.SchedulerScoreWeights.PreviousResponse,
			SessionSticky: s.cfg.Gateway.OpenAIWS.SchedulerScoreWeights.SessionSticky,
		}
	}
	return GatewayOpenAIWSSchedulerScoreWeightsView{
		Priority:      1.0,
		Load:          1.0,
		Queue:         0.7,
		ErrorRate:     0.8,
		TTFT:          0.5,
		Reset:         0.0,
		QuotaHeadroom: 0.0,
		UpstreamCost:  0.0,
		Previous:      5.0,
		SessionSticky: 3.0,
	}
}

func (s *OpenAIGatewayService) openAIWSSchedulerWeightsForRequest(ctx context.Context) GatewayOpenAIWSSchedulerScoreWeightsView {
	weights := s.openAIWSSchedulerWeights()
	settings := s.openAIAdvancedSchedulerRuntimeSettings(ctx)
	// 同 openAIWSLBTopKForRequest：总开关关闭时不应用 DB 覆盖值。
	if !settings.enabled {
		return weights
	}
	overridden := applyOpenAIAdvancedSchedulerWeightOverrides(weights, settings.weightOverrides)
	if !overridden.configWeights().IsValid() {
		return weights
	}
	return overridden
}

func applyOpenAIAdvancedSchedulerWeightOverrides(
	weights GatewayOpenAIWSSchedulerScoreWeightsView,
	overrides map[string]float64,
) GatewayOpenAIWSSchedulerScoreWeightsView {
	for key, value := range overrides {
		switch key {
		case "priority":
			weights.Priority = value
		case "load":
			weights.Load = value
		case "queue":
			weights.Queue = value
		case "error_rate":
			weights.ErrorRate = value
		case "ttft":
			weights.TTFT = value
		case "reset":
			weights.Reset = value
		case "quota_headroom":
			weights.QuotaHeadroom = value
		case "upstream_cost":
			weights.UpstreamCost = value
		case "previous_response":
			weights.Previous = value
		case "session_sticky":
			weights.SessionSticky = value
		}
	}
	return weights
}

type GatewayOpenAIWSSchedulerScoreWeightsView struct {
	Priority  float64
	Load      float64
	Queue     float64
	ErrorRate float64
	TTFT      float64
	// Reset 倾向「会话窗口最早重置」的账号；0 表示关闭（默认）。
	Reset         float64
	QuotaHeadroom float64
	UpstreamCost  float64
	Previous      float64
	SessionSticky float64
}

func (w GatewayOpenAIWSSchedulerScoreWeightsView) configWeights() config.GatewayOpenAIWSSchedulerScoreWeights {
	return config.GatewayOpenAIWSSchedulerScoreWeights{
		Priority:         w.Priority,
		Load:             w.Load,
		Queue:            w.Queue,
		ErrorRate:        w.ErrorRate,
		TTFT:             w.TTFT,
		Reset:            w.Reset,
		QuotaHeadroom:    w.QuotaHeadroom,
		UpstreamCost:     w.UpstreamCost,
		PreviousResponse: w.Previous,
		SessionSticky:    w.SessionSticky,
	}
}

type OpenAIAccountSchedulerScoreSnapshot struct {
	BaseScore             float64
	StickyScore           float64
	StickyScoreInfinity   bool
	StickyWeightedEnabled bool
}

func (s *RateLimitService) BuildOpenAIAccountSchedulerScoreSnapshot(
	ctx context.Context,
	accounts []*Account,
	loadMap map[int64]*AccountLoadInfo,
) map[int64]OpenAIAccountSchedulerScoreSnapshot {
	gateway := &OpenAIGatewayService{cfg: nil, rateLimitService: s}
	if s != nil {
		gateway.cfg = s.cfg
	}
	return buildOpenAIAccountSchedulerScoreSnapshot(
		accounts,
		loadMap,
		gateway.openAIWSSchedulerWeightsForRequest(ctx),
		gateway.isOpenAIAdvancedSchedulerStickyWeightedEnabled(ctx),
		gateway.openAIOAuthSchedulingRateMultiplier(ctx),
	)
}

func BuildOpenAIAccountSchedulerScoreSnapshot(
	accounts []*Account,
	loadMap map[int64]*AccountLoadInfo,
) map[int64]OpenAIAccountSchedulerScoreSnapshot {
	gateway := &OpenAIGatewayService{}
	return buildOpenAIAccountSchedulerScoreSnapshot(accounts, loadMap, gateway.openAIWSSchedulerWeights(), false, defaultOpenAIOAuthSchedulingRateMultiplier)
}

func buildOpenAIAccountSchedulerScoreSnapshot(
	accounts []*Account,
	loadMap map[int64]*AccountLoadInfo,
	weights GatewayOpenAIWSSchedulerScoreWeightsView,
	stickyWeightedEnabled bool,
	oauthSchedulingRateMultiplier float64,
) map[int64]OpenAIAccountSchedulerScoreSnapshot {
	if len(accounts) == 0 {
		return nil
	}
	candidates := make([]openAIAccountCandidateScore, 0, len(accounts))
	for _, account := range accounts {
		if account == nil {
			continue
		}
		loadInfo := loadMap[account.ID]
		if loadInfo == nil {
			loadInfo = &AccountLoadInfo{AccountID: account.ID}
		}
		candidates = append(candidates, openAIAccountCandidateScore{
			account:   account,
			loadInfo:  loadInfo,
			errorRate: 0,
			ttft:      0,
			hasTTFT:   false,
		})
	}
	if len(candidates) == 0 {
		return nil
	}

	minPriority, maxPriority := openAIAccountSchedulingPriority(candidates[0].account), openAIAccountSchedulingPriority(candidates[0].account)
	maxWaiting := 1
	for i := range candidates {
		candidate := &candidates[i]
		candidate.priority = openAIAccountSchedulingPriority(candidate.account)
		if candidate.priority < minPriority {
			minPriority = candidate.priority
		}
		if candidate.priority > maxPriority {
			maxPriority = candidate.priority
		}
		if candidate.loadInfo.WaitingCount > maxWaiting {
			maxWaiting = candidate.loadInfo.WaitingCount
		}
	}

	minResetRemaining, maxResetRemaining := 0.0, 0.0
	hasResetSample := false
	now := time.Now()
	upstreamCostFactors := map[int64]float64(nil)
	if weights.UpstreamCost > 0 {
		accounts := make([]*Account, 0, len(candidates))
		for _, candidate := range candidates {
			accounts = append(accounts, candidate.account)
		}
		upstreamCostFactors = openAIUpstreamCostFactors(accounts, now, oauthSchedulingRateMultiplier)
	}
	if weights.Reset > 0 {
		for _, candidate := range candidates {
			end := candidate.account.SessionWindowEnd
			if end == nil || !now.Before(*end) {
				continue
			}
			remaining := end.Sub(now).Seconds()
			if !hasResetSample {
				minResetRemaining, maxResetRemaining = remaining, remaining
				hasResetSample = true
				continue
			}
			if remaining < minResetRemaining {
				minResetRemaining = remaining
			}
			if remaining > maxResetRemaining {
				maxResetRemaining = remaining
			}
		}
	}

	result := make(map[int64]OpenAIAccountSchedulerScoreSnapshot, len(candidates))
	for _, candidate := range candidates {
		priorityFactor := 1.0
		if maxPriority > minPriority {
			priorityFactor = 1 - float64(candidate.priority-minPriority)/float64(maxPriority-minPriority)
		}
		loadFactor := 1 - clamp01(float64(candidate.loadInfo.LoadRate)/100.0)
		queueFactor := 1 - clamp01(float64(candidate.loadInfo.WaitingCount)/float64(maxWaiting))
		errorFactor := 1.0
		ttftFactor := 0.5
		resetFactor := 0.0
		if weights.Reset > 0 && hasResetSample {
			if end := candidate.account.SessionWindowEnd; end != nil && now.Before(*end) {
				if maxResetRemaining > minResetRemaining {
					resetFactor = 1 - clamp01((end.Sub(now).Seconds()-minResetRemaining)/(maxResetRemaining-minResetRemaining))
				} else {
					resetFactor = 1
				}
			}
		}
		quotaHeadroomFactor := 0.0
		if weights.QuotaHeadroom > 0 {
			quotaHeadroomFactor = openAIQuotaHeadroomFactor(candidate.account, now)
		}
		upstreamCostFactor := openAIUpstreamCostNeutralFactor
		if factor, ok := upstreamCostFactors[candidate.account.ID]; ok {
			upstreamCostFactor = factor
		}
		baseScore := weights.Priority*priorityFactor +
			weights.Load*loadFactor +
			weights.Queue*queueFactor +
			weights.ErrorRate*errorFactor +
			weights.TTFT*ttftFactor +
			weights.Reset*resetFactor +
			weights.QuotaHeadroom*quotaHeadroomFactor +
			weights.UpstreamCost*(upstreamCostFactor-openAIUpstreamCostNeutralFactor)
		score := OpenAIAccountSchedulerScoreSnapshot{
			BaseScore:             baseScore,
			StickyWeightedEnabled: stickyWeightedEnabled,
			StickyScoreInfinity:   !stickyWeightedEnabled,
		}
		if stickyWeightedEnabled {
			score.StickyScore = baseScore + weights.Previous + weights.SessionSticky
		}
		result[candidate.account.ID] = score
	}
	return result
}

func openAIUpstreamCostFactors(accounts []*Account, now time.Time, oauthSchedulingRateMultiplier float64) map[int64]float64 {
	type rateSample struct {
		accountID int64
		rate      float64
	}

	factors := make(map[int64]float64, len(accounts))
	samples := make([]rateSample, 0, len(accounts))
	eligibleCount := 0
	for _, account := range accounts {
		if account == nil {
			continue
		}
		factors[account.ID] = openAIUpstreamCostNeutralFactor
		if !account.IsOpenAIApiKey() && !account.IsOpenAIOAuth() {
			continue
		}
		eligibleCount++
		if rate, ok := openAISchedulingRate(account, now, oauthSchedulingRateMultiplier); ok {
			samples = append(samples, rateSample{accountID: account.ID, rate: rate})
		}
	}
	if len(samples) < 2 || eligibleCount == 0 {
		return factors
	}

	allEqual := true
	positiveLogs := make([]float64, 0, len(samples))
	for i, sample := range samples {
		if i > 0 && sample.rate != samples[0].rate {
			allEqual = false
		}
		if sample.rate > 0 {
			positiveLogs = append(positiveLogs, math.Log(sample.rate))
		}
	}
	if allEqual || len(positiveLogs) == 0 {
		return factors
	}

	sort.Float64s(positiveLogs)
	middle := len(positiveLogs) / 2
	medianLog := positiveLogs[middle]
	if len(positiveLogs)%2 == 0 {
		medianLog = (positiveLogs[middle-1] + positiveLogs[middle]) / 2
	}
	center := math.Exp(medianLog)
	if center <= 0 || math.IsNaN(center) || math.IsInf(center, 0) {
		return factors
	}

	coverage := float64(len(samples)) / float64(eligibleCount)
	for _, sample := range samples {
		rawFactor := 1.0
		if sample.rate > 0 {
			rawFactor = 1 / (1 + sample.rate/center)
		}
		factors[sample.accountID] = clamp01(openAIUpstreamCostNeutralFactor + coverage*(rawFactor-openAIUpstreamCostNeutralFactor))
	}
	return factors
}

type openAILegacyUpstreamRateOrder struct {
	enabled bool
	rates   map[int64]float64
}

func newOpenAILegacyUpstreamRateOrder(accounts []*Account, now time.Time, oauthSchedulingRateMultiplier float64) openAILegacyUpstreamRateOrder {
	rates := make(map[int64]float64, len(accounts))
	var first float64
	distinct := false
	for _, account := range accounts {
		if account == nil {
			continue
		}
		// 与 openAIUpstreamCostFactors 使用同一道平台门控：只有 OpenAI 平台账号
		// 的倍率参与 legacy 低倍率优先排序。上游自报倍率来自中转方，不能让它对
		// 其他平台的调度产生影响——否则自报低价即可吸走流量，而实际结算走本地倍率。
		if !account.IsOpenAIApiKey() && !account.IsOpenAIOAuth() {
			continue
		}
		rate, ok := openAISchedulingRate(account, now, oauthSchedulingRateMultiplier)
		if !ok {
			continue
		}
		if len(rates) == 0 {
			first = rate
		} else if rate != first {
			distinct = true
		}
		rates[account.ID] = rate
	}
	return openAILegacyUpstreamRateOrder{enabled: len(rates) >= 2 && distinct, rates: rates}
}

func openAISchedulingRate(account *Account, now time.Time, oauthSchedulingRateMultiplier float64) (float64, bool) {
	if account != nil && account.IsOpenAIOAuth() {
		return oauthSchedulingRateMultiplier, true
	}
	return openAIFreshUpstreamBillingRate(account, now)
}

// compare returns -1 when a should be selected before b, 1 when b should be
// selected first, and 0 when the rate signal does not distinguish them.
func (o openAILegacyUpstreamRateOrder) compare(a, b *Account) int {
	if !o.enabled || a == nil || b == nil {
		return 0
	}
	aRate, aKnown := o.rates[a.ID]
	bRate, bKnown := o.rates[b.ID]
	if aKnown != bKnown {
		if aKnown {
			return -1
		}
		return 1
	}
	if !aKnown || aRate == bRate {
		return 0
	}
	if aRate < bRate {
		return -1
	}
	return 1
}

func openAIFreshUpstreamBillingRate(account *Account, now time.Time) (float64, bool) {
	if !isUpstreamBillingProbeAccount(account) {
		return 0, false
	}
	snapshot := decodeUpstreamBillingProbeSnapshot(account.Extra)
	if snapshot == nil || (snapshot.Status != UpstreamBillingProbeStatusOK && snapshot.Status != UpstreamBillingProbeStatusFailed) ||
		snapshot.ReceivedAt == nil || snapshot.ReceivedAt.IsZero() {
		return 0, false
	}
	receivedAt := *snapshot.ReceivedAt
	freshUntil := snapshot.FreshUntil
	if freshUntil == nil && snapshot.Status == UpstreamBillingProbeStatusOK {
		interval := snapshot.NextProbeAt.Sub(receivedAt)
		if interval > 0 {
			freshUntil = probeTimePtr(receivedAt.Add(2 * interval))
		}
	}
	if freshUntil == nil || !freshUntil.After(receivedAt) || now.Before(receivedAt) || now.After(*freshUntil) {
		return 0, false
	}
	return upstreamBillingRateAt(snapshot.Data, now)
}

func openAIQuotaHeadroomFactor(account *Account, now time.Time) float64 {
	if account == nil || len(account.Extra) == 0 || openAIQuotaHeadroomSnapshotStale(account.Extra, now) {
		return openAIQuotaHeadroomNeutralFactor
	}
	primaryUsedPercent, ok := resolveAccountExtraNumber(account.Extra, "codex_primary_used_percent", "codex_7d_used_percent")
	if !ok || openAIQuotaWindowResetAny(account.Extra, now, "primary", "7d") {
		return openAIQuotaHeadroomNeutralFactor
	}

	factor := 1 - clamp01(primaryUsedPercent/100)
	if secondaryUsedPercent, ok := resolveAccountExtraNumber(account.Extra, "codex_secondary_used_percent", "codex_5h_used_percent"); ok &&
		!openAIQuotaWindowResetAny(account.Extra, now, "secondary", "5h") {
		secondaryRemaining := 1 - clamp01(secondaryUsedPercent/100)
		if secondaryRemaining < openAIQuotaHeadroomSecondaryLowRemain {
			factor *= openAIQuotaHeadroomNeutralFactor
		}
	}
	return factor
}

func openAIQuotaHeadroomSnapshotStale(extra map[string]any, now time.Time) bool {
	updatedRaw, ok := extra["codex_usage_updated_at"]
	if !ok {
		return true
	}
	updatedAt, err := parseTime(fmt.Sprint(updatedRaw))
	if err != nil {
		return true
	}
	return now.Sub(updatedAt) >= openAIQuotaHeadroomSnapshotStaleAfter
}

func openAIQuotaWindowResetAny(extra map[string]any, now time.Time, windows ...string) bool {
	for _, window := range windows {
		if openAIQuotaWindowReset(extra, window, now) {
			return true
		}
	}
	return false
}

func clamp01(value float64) float64 {
	switch {
	case value < 0:
		return 0
	case value > 1:
		return 1
	default:
		return value
	}
}

func calcLoadSkewByMoments(sum float64, sumSquares float64, count int) float64 {
	if count <= 1 {
		return 0
	}
	mean := sum / float64(count)
	variance := sumSquares/float64(count) - mean*mean
	if variance < 0 {
		variance = 0
	}
	return math.Sqrt(variance)
}