package service

import (
	"bufio"
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log"
	"log/slog"
	mathrand "math/rand"
	"net/http"
	"os"
	"regexp"
	"sort"
	"strings"
	"sync/atomic"
	"time"

	"github.com/Wei-Shaw/sub2api/internal/config"
	"github.com/Wei-Shaw/sub2api/internal/pkg/claude"
	"github.com/Wei-Shaw/sub2api/internal/pkg/ctxkey"
	"github.com/Wei-Shaw/sub2api/internal/util/responseheaders"
	"github.com/Wei-Shaw/sub2api/internal/util/urlvalidator"
	"github.com/google/uuid"
	"github.com/tidwall/gjson"
	"github.com/tidwall/sjson"

	"github.com/gin-gonic/gin"
)

const (
	claudeAPIURL            = "https://api.anthropic.com/v1/messages?beta=true"
	claudeAPICountTokensURL = "https://api.anthropic.com/v1/messages/count_tokens?beta=true"
	stickySessionTTL        = time.Hour // 粘性会话TTL
	defaultMaxLineSize      = 40 * 1024 * 1024
	// Canonical Claude Code banner. Keep it EXACT (no trailing whitespace/newlines)
	// to match real Claude CLI traffic as closely as possible. When we need a visual
	// separator between system blocks, we add "\n\n" at concatenation time.
	claudeCodeSystemPrompt = "You are Claude Code, Anthropic's official CLI for Claude."
	maxCacheControlBlocks  = 4 // Anthropic API 允许的最大 cache_control 块数量
)

const (
	claudeMimicDebugInfoKey = "claude_mimic_debug_info"
)

// ForceCacheBillingContextKey 强制缓存计费上下文键
// 用于粘性会话切换时，将 input_tokens 转为 cache_read_input_tokens 计费
type forceCacheBillingKeyType struct{}

// accountWithLoad 账号与负载信息的组合，用于负载感知调度
type accountWithLoad struct {
	account  *Account
	loadInfo *AccountLoadInfo
}

var ForceCacheBillingContextKey = forceCacheBillingKeyType{}

// IsForceCacheBilling 检查是否启用强制缓存计费
func IsForceCacheBilling(ctx context.Context) bool {
	v, _ := ctx.Value(ForceCacheBillingContextKey).(bool)
	return v
}

// WithForceCacheBilling 返回带有强制缓存计费标记的上下文
func WithForceCacheBilling(ctx context.Context) context.Context {
	return context.WithValue(ctx, ForceCacheBillingContextKey, true)
}

func (s *GatewayService) debugModelRoutingEnabled() bool {
	v := strings.ToLower(strings.TrimSpace(os.Getenv("SUB2API_DEBUG_MODEL_ROUTING")))
	return v == "1" || v == "true" || v == "yes" || v == "on"
}

func (s *GatewayService) debugClaudeMimicEnabled() bool {
	v := strings.ToLower(strings.TrimSpace(os.Getenv("SUB2API_DEBUG_CLAUDE_MIMIC")))
	return v == "1" || v == "true" || v == "yes" || v == "on"
}

func shortSessionHash(sessionHash string) string {
	if sessionHash == "" {
		return ""
	}
	if len(sessionHash) <= 8 {
		return sessionHash
	}
	return sessionHash[:8]
}

func redactAuthHeaderValue(v string) string {
	v = strings.TrimSpace(v)
	if v == "" {
		return ""
	}
	// Keep scheme for debugging, redact secret.
	if strings.HasPrefix(strings.ToLower(v), "bearer ") {
		return "Bearer [redacted]"
	}
	return "[redacted]"
}

func safeHeaderValueForLog(key string, v string) string {
	key = strings.ToLower(strings.TrimSpace(key))
	switch key {
	case "authorization", "x-api-key":
		return redactAuthHeaderValue(v)
	default:
		return strings.TrimSpace(v)
	}
}

func extractSystemPreviewFromBody(body []byte) string {
	if len(body) == 0 {
		return ""
	}
	sys := gjson.GetBytes(body, "system")
	if !sys.Exists() {
		return ""
	}

	switch {
	case sys.IsArray():
		for _, item := range sys.Array() {
			if !item.IsObject() {
				continue
			}
			if strings.EqualFold(item.Get("type").String(), "text") {
				if t := item.Get("text").String(); strings.TrimSpace(t) != "" {
					return t
				}
			}
		}
		return ""
	case sys.Type == gjson.String:
		return sys.String()
	default:
		return ""
	}
}

func buildClaudeMimicDebugLine(req *http.Request, body []byte, account *Account, tokenType string, mimicClaudeCode bool) string {
	if req == nil {
		return ""
	}

	// Only log a minimal fingerprint to avoid leaking user content.
	interesting := []string{
		"user-agent",
		"x-app",
		"anthropic-dangerous-direct-browser-access",
		"anthropic-version",
		"anthropic-beta",
		"x-stainless-lang",
		"x-stainless-package-version",
		"x-stainless-os",
		"x-stainless-arch",
		"x-stainless-runtime",
		"x-stainless-runtime-version",
		"x-stainless-retry-count",
		"x-stainless-timeout",
		"authorization",
		"x-api-key",
		"content-type",
		"accept",
		"x-stainless-helper-method",
	}

	h := make([]string, 0, len(interesting))
	for _, k := range interesting {
		if v := req.Header.Get(k); v != "" {
			h = append(h, fmt.Sprintf("%s=%q", k, safeHeaderValueForLog(k, v)))
		}
	}

	metaUserID := strings.TrimSpace(gjson.GetBytes(body, "metadata.user_id").String())
	sysPreview := strings.TrimSpace(extractSystemPreviewFromBody(body))

	// Truncate preview to keep logs sane.
	if len(sysPreview) > 300 {
		sysPreview = sysPreview[:300] + "..."
	}
	sysPreview = strings.ReplaceAll(sysPreview, "\n", "\\n")
	sysPreview = strings.ReplaceAll(sysPreview, "\r", "\\r")

	aid := int64(0)
	aname := ""
	if account != nil {
		aid = account.ID
		aname = account.Name
	}

	return fmt.Sprintf(
		"url=%s account=%d(%s) tokenType=%s mimic=%t meta.user_id=%q system.preview=%q headers={%s}",
		req.URL.String(),
		aid,
		aname,
		tokenType,
		mimicClaudeCode,
		metaUserID,
		sysPreview,
		strings.Join(h, " "),
	)
}

func logClaudeMimicDebug(req *http.Request, body []byte, account *Account, tokenType string, mimicClaudeCode bool) {
	line := buildClaudeMimicDebugLine(req, body, account, tokenType, mimicClaudeCode)
	if line == "" {
		return
	}
	log.Printf("[ClaudeMimicDebug] %s", line)
}

func isClaudeCodeCredentialScopeError(msg string) bool {
	m := strings.ToLower(strings.TrimSpace(msg))
	if m == "" {
		return false
	}
	return strings.Contains(m, "only authorized for use with claude code") &&
		strings.Contains(m, "cannot be used for other api requests")
}

// sseDataRe matches SSE data lines with optional whitespace after colon.
// Some upstream APIs return non-standard "data:" without space (should be "data: ").
var (
	sseDataRe            = regexp.MustCompile(`^data:\s*`)
	sessionIDRegex       = regexp.MustCompile(`session_([a-f0-9-]{36})`)
	claudeCliUserAgentRe = regexp.MustCompile(`^claude-cli/\d+\.\d+\.\d+`)

	// claudeCodePromptPrefixes 用于检测 Claude Code 系统提示词的前缀列表
	// 支持多种变体：标准版、Agent SDK 版、Explore Agent 版、Compact 版等
	// 注意：前缀之间不应存在包含关系，否则会导致冗余匹配
	claudeCodePromptPrefixes = []string{
		"You are Claude Code, Anthropic's official CLI for Claude",             // 标准版 & Agent SDK 版（含 running within...）
		"You are a Claude agent, built on Anthropic's Claude Agent SDK",        // Agent SDK 变体
		"You are a file search specialist for Claude Code",                     // Explore Agent 版
		"You are a helpful AI assistant tasked with summarizing conversations", // Compact 版
	}
)

// ErrClaudeCodeOnly 表示分组仅允许 Claude Code 客户端访问
var ErrClaudeCodeOnly = errors.New("this group only allows Claude Code clients")

// ErrModelScopeNotSupported 表示请求的模型系列不在分组支持的范围内
var ErrModelScopeNotSupported = errors.New("model scope not supported by this group")

// allowedHeaders 白名单headers（参考CRS项目）
var allowedHeaders = map[string]bool{
	"accept":                                    true,
	"x-stainless-retry-count":                   true,
	"x-stainless-timeout":                       true,
	"x-stainless-lang":                          true,
	"x-stainless-package-version":               true,
	"x-stainless-os":                            true,
	"x-stainless-arch":                          true,
	"x-stainless-runtime":                       true,
	"x-stainless-runtime-version":               true,
	"x-stainless-helper-method":                 true,
	"anthropic-dangerous-direct-browser-access": true,
	"anthropic-version":                         true,
	"x-app":                                     true,
	"anthropic-beta":                            true,
	"accept-language":                           true,
	"sec-fetch-mode":                            true,
	"user-agent":                                true,
	"content-type":                              true,
}

// GatewayCache 定义网关服务的缓存操作接口。
// 提供粘性会话（Sticky Session）的存储、查询、刷新和删除功能。
//
// ModelLoadInfo 模型负载信息（用于 Antigravity 调度）
// Model load info for Antigravity scheduling
type ModelLoadInfo struct {
	CallCount  int64     // 当前分钟调用次数 / Call count in current minute
	LastUsedAt time.Time // 最后调度时间（零值表示未调度过）/ Last scheduling time (zero means never scheduled)
}

// GatewayCache defines cache operations for gateway service.
// Provides sticky session storage, retrieval, refresh and deletion capabilities.
type GatewayCache interface {
	// GetSessionAccountID 获取粘性会话绑定的账号 ID
	// Get the account ID bound to a sticky session
	GetSessionAccountID(ctx context.Context, groupID int64, sessionHash string) (int64, error)
	// SetSessionAccountID 设置粘性会话与账号的绑定关系
	// Set the binding between sticky session and account
	SetSessionAccountID(ctx context.Context, groupID int64, sessionHash string, accountID int64, ttl time.Duration) error
	// RefreshSessionTTL 刷新粘性会话的过期时间
	// Refresh the expiration time of a sticky session
	RefreshSessionTTL(ctx context.Context, groupID int64, sessionHash string, ttl time.Duration) error
	// DeleteSessionAccountID 删除粘性会话绑定，用于账号不可用时主动清理
	// Delete sticky session binding, used to proactively clean up when account becomes unavailable
	DeleteSessionAccountID(ctx context.Context, groupID int64, sessionHash string) error

	// IncrModelCallCount 增加模型调用次数并更新最后调度时间（Antigravity 专用）
	// Increment model call count and update last scheduling time (Antigravity only)
	// 返回更新后的调用次数
	IncrModelCallCount(ctx context.Context, accountID int64, model string) (int64, error)

	// GetModelLoadBatch 批量获取账号的模型负载信息（Antigravity 专用）
	// Batch get model load info for accounts (Antigravity only)
	GetModelLoadBatch(ctx context.Context, accountIDs []int64, model string) (map[int64]*ModelLoadInfo, error)

	// FindGeminiSession 查找 Gemini 会话（MGET 倒序匹配）
	// Find Gemini session using MGET reverse order matching
	// 返回最长匹配的会话信息（uuid, accountID）
	FindGeminiSession(ctx context.Context, groupID int64, prefixHash, digestChain string) (uuid string, accountID int64, found bool)

	// SaveGeminiSession 保存 Gemini 会话
	// Save Gemini session binding
	SaveGeminiSession(ctx context.Context, groupID int64, prefixHash, digestChain, uuid string, accountID int64) error
}

// derefGroupID safely dereferences *int64 to int64, returning 0 if nil
func derefGroupID(groupID *int64) int64 {
	if groupID == nil {
		return 0
	}
	return *groupID
}

// stickySessionRateLimitThreshold 定义清除粘性会话的限流时间阈值。
// 当账号限流剩余时间超过此阈值时，清除粘性会话以便切换到其他账号。
// 低于此阈值时保持粘性会话，等待短暂限流结束。
const stickySessionRateLimitThreshold = 10 * time.Second

// shouldClearStickySession 检查账号是否处于不可调度状态，需要清理粘性会话绑定。
// 当账号状态为错误、禁用、不可调度、处于临时不可调度期间，
// 或模型限流剩余时间超过 stickySessionRateLimitThreshold 时，返回 true。
// 这确保后续请求不会继续使用不可用的账号。
//
// shouldClearStickySession checks if an account is in an unschedulable state
// and the sticky session binding should be cleared.
// Returns true when account status is error/disabled, schedulable is false,
// within temporary unschedulable period, or model rate limit remaining time
// exceeds stickySessionRateLimitThreshold.
// This ensures subsequent requests won't continue using unavailable accounts.
func shouldClearStickySession(account *Account, requestedModel string) bool {
	if account == nil {
		return false
	}
	if account.Status == StatusError || account.Status == StatusDisabled || !account.Schedulable {
		return true
	}
	if account.TempUnschedulableUntil != nil && time.Now().Before(*account.TempUnschedulableUntil) {
		return true
	}
	// 检查模型限流和 scope 限流，只在超过阈值时清除粘性会话
	if remaining := account.GetRateLimitRemainingTimeWithContext(context.Background(), requestedModel); remaining > stickySessionRateLimitThreshold {
		return true
	}
	return false
}

type AccountWaitPlan struct {
	AccountID      int64
	MaxConcurrency int
	Timeout        time.Duration
	MaxWaiting     int
}

type AccountSelectionResult struct {
	Account     *Account
	Acquired    bool
	ReleaseFunc func()
	WaitPlan    *AccountWaitPlan // nil means no wait allowed
}

// ClaudeUsage 表示Claude API返回的usage信息
type ClaudeUsage struct {
	InputTokens              int `json:"input_tokens"`
	OutputTokens             int `json:"output_tokens"`
	CacheCreationInputTokens int `json:"cache_creation_input_tokens"`
	CacheReadInputTokens     int `json:"cache_read_input_tokens"`
}

// ForwardResult 转发结果
type ForwardResult struct {
	RequestID        string
	Usage            ClaudeUsage
	Model            string
	Stream           bool
	Duration         time.Duration
	FirstTokenMs     *int // 首字时间（流式请求）
	ClientDisconnect bool // 客户端是否在流式传输过程中断开

	// 图片生成计费字段（仅 gemini-3-pro-image 使用）
	ImageCount int    // 生成的图片数量
	ImageSize  string // 图片尺寸 "1K", "2K", "4K"

	// Sora 媒体字段
	MediaType string // image / video / prompt
	MediaURL  string // 生成后的媒体地址（可选）
}

// UpstreamFailoverError indicates an upstream error that should trigger account failover.
type UpstreamFailoverError struct {
	StatusCode        int
	ResponseBody      []byte // 上游响应体，用于错误透传规则匹配
	ForceCacheBilling bool   // Antigravity 粘性会话切换时设为 true
}

func (e *UpstreamFailoverError) Error() string {
	return fmt.Sprintf("upstream error: %d (failover)", e.StatusCode)
}

// GatewayService handles API gateway operations
type GatewayService struct {
	accountRepo         AccountRepository
	groupRepo           GroupRepository
	usageLogRepo        UsageLogRepository
	userRepo            UserRepository
	userSubRepo         UserSubscriptionRepository
	userGroupRateRepo   UserGroupRateRepository
	cache               GatewayCache
	cfg                 *config.Config
	schedulerSnapshot   *SchedulerSnapshotService
	billingService      *BillingService
	rateLimitService    *RateLimitService
	billingCacheService *BillingCacheService
	identityService     *IdentityService
	httpUpstream        HTTPUpstream
	deferredService     *DeferredService
	concurrencyService  *ConcurrencyService
	claudeTokenProvider *ClaudeTokenProvider
	sessionLimitCache   SessionLimitCache // 会话数量限制缓存（仅 Anthropic OAuth/SetupToken）
}

// NewGatewayService creates a new GatewayService
func NewGatewayService(
	accountRepo AccountRepository,
	groupRepo GroupRepository,
	usageLogRepo UsageLogRepository,
	userRepo UserRepository,
	userSubRepo UserSubscriptionRepository,
	userGroupRateRepo UserGroupRateRepository,
	cache GatewayCache,
	cfg *config.Config,
	schedulerSnapshot *SchedulerSnapshotService,
	concurrencyService *ConcurrencyService,
	billingService *BillingService,
	rateLimitService *RateLimitService,
	billingCacheService *BillingCacheService,
	identityService *IdentityService,
	httpUpstream HTTPUpstream,
	deferredService *DeferredService,
	claudeTokenProvider *ClaudeTokenProvider,
	sessionLimitCache SessionLimitCache,
) *GatewayService {
	return &GatewayService{
		accountRepo:         accountRepo,
		groupRepo:           groupRepo,
		usageLogRepo:        usageLogRepo,
		userRepo:            userRepo,
		userSubRepo:         userSubRepo,
		userGroupRateRepo:   userGroupRateRepo,
		cache:               cache,
		cfg:                 cfg,
		schedulerSnapshot:   schedulerSnapshot,
		concurrencyService:  concurrencyService,
		billingService:      billingService,
		rateLimitService:    rateLimitService,
		billingCacheService: billingCacheService,
		identityService:     identityService,
		httpUpstream:        httpUpstream,
		deferredService:     deferredService,
		claudeTokenProvider: claudeTokenProvider,
		sessionLimitCache:   sessionLimitCache,
	}
}

// GenerateSessionHash 从预解析请求计算粘性会话 hash
func (s *GatewayService) GenerateSessionHash(parsed *ParsedRequest) string {
	if parsed == nil {
		return ""
	}

	// 1. 最高优先级：从 metadata.user_id 提取 session_xxx
	if parsed.MetadataUserID != "" {
		if match := sessionIDRegex.FindStringSubmatch(parsed.MetadataUserID); len(match) > 1 {
			return match[1]
		}
	}

	// 2. 提取带 cache_control: {type: "ephemeral"} 的内容
	cacheableContent := s.extractCacheableContent(parsed)
	if cacheableContent != "" {
		return s.hashContent(cacheableContent)
	}

	// 3. Fallback: 使用 system 内容
	if parsed.System != nil {
		systemText := s.extractTextFromSystem(parsed.System)
		if systemText != "" {
			return s.hashContent(systemText)
		}
	}

	// 4. 最后 fallback: 使用第一条消息
	if len(parsed.Messages) > 0 {
		if firstMsg, ok := parsed.Messages[0].(map[string]any); ok {
			msgText := s.extractTextFromContent(firstMsg["content"])
			if msgText != "" {
				return s.hashContent(msgText)
			}
		}
	}

	return ""
}

// BindStickySession sets session -> account binding with standard TTL.
func (s *GatewayService) BindStickySession(ctx context.Context, groupID *int64, sessionHash string, accountID int64) error {
	if sessionHash == "" || accountID <= 0 || s.cache == nil {
		return nil
	}
	return s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, accountID, stickySessionTTL)
}

// GetCachedSessionAccountID retrieves the account ID bound to a sticky session.
// Returns 0 if no binding exists or on error.
func (s *GatewayService) GetCachedSessionAccountID(ctx context.Context, groupID *int64, sessionHash string) (int64, error) {
	if sessionHash == "" || s.cache == nil {
		return 0, nil
	}
	accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
	if err != nil {
		return 0, err
	}
	return accountID, nil
}

// FindGeminiSession 查找 Gemini 会话（基于内容摘要链的 Fallback 匹配）
// 返回最长匹配的会话信息（uuid, accountID）
func (s *GatewayService) FindGeminiSession(ctx context.Context, groupID int64, prefixHash, digestChain string) (uuid string, accountID int64, found bool) {
	if digestChain == "" || s.cache == nil {
		return "", 0, false
	}
	return s.cache.FindGeminiSession(ctx, groupID, prefixHash, digestChain)
}

// SaveGeminiSession 保存 Gemini 会话
func (s *GatewayService) SaveGeminiSession(ctx context.Context, groupID int64, prefixHash, digestChain, uuid string, accountID int64) error {
	if digestChain == "" || s.cache == nil {
		return nil
	}
	return s.cache.SaveGeminiSession(ctx, groupID, prefixHash, digestChain, uuid, accountID)
}

func (s *GatewayService) extractCacheableContent(parsed *ParsedRequest) string {
	if parsed == nil {
		return ""
	}

	var builder strings.Builder

	// 检查 system 中的 cacheable 内容
	if system, ok := parsed.System.([]any); ok {
		for _, part := range system {
			if partMap, ok := part.(map[string]any); ok {
				if cc, ok := partMap["cache_control"].(map[string]any); ok {
					if cc["type"] == "ephemeral" {
						if text, ok := partMap["text"].(string); ok {
							_, _ = builder.WriteString(text)
						}
					}
				}
			}
		}
	}
	systemText := builder.String()

	// 检查 messages 中的 cacheable 内容
	for _, msg := range parsed.Messages {
		if msgMap, ok := msg.(map[string]any); ok {
			if msgContent, ok := msgMap["content"].([]any); ok {
				for _, part := range msgContent {
					if partMap, ok := part.(map[string]any); ok {
						if cc, ok := partMap["cache_control"].(map[string]any); ok {
							if cc["type"] == "ephemeral" {
								return s.extractTextFromContent(msgMap["content"])
							}
						}
					}
				}
			}
		}
	}

	return systemText
}

func (s *GatewayService) extractTextFromSystem(system any) string {
	switch v := system.(type) {
	case string:
		return v
	case []any:
		var texts []string
		for _, part := range v {
			if partMap, ok := part.(map[string]any); ok {
				if text, ok := partMap["text"].(string); ok {
					texts = append(texts, text)
				}
			}
		}
		return strings.Join(texts, "")
	}
	return ""
}

func (s *GatewayService) extractTextFromContent(content any) string {
	switch v := content.(type) {
	case string:
		return v
	case []any:
		var texts []string
		for _, part := range v {
			if partMap, ok := part.(map[string]any); ok {
				if partMap["type"] == "text" {
					if text, ok := partMap["text"].(string); ok {
						texts = append(texts, text)
					}
				}
			}
		}
		return strings.Join(texts, "")
	}
	return ""
}

func (s *GatewayService) hashContent(content string) string {
	hash := sha256.Sum256([]byte(content))
	return hex.EncodeToString(hash[:16]) // 32字符
}

// replaceModelInBody 替换请求体中的model字段
// 使用 json.RawMessage 保留其他字段的原始字节，避免 thinking 块等内容被修改
func (s *GatewayService) replaceModelInBody(body []byte, newModel string) []byte {
	var req map[string]json.RawMessage
	if err := json.Unmarshal(body, &req); err != nil {
		return body
	}
	// 只序列化 model 字段
	modelBytes, err := json.Marshal(newModel)
	if err != nil {
		return body
	}
	req["model"] = modelBytes
	newBody, err := json.Marshal(req)
	if err != nil {
		return body
	}
	return newBody
}

type claudeOAuthNormalizeOptions struct {
	injectMetadata          bool
	metadataUserID          string
	stripSystemCacheControl bool
}

// sanitizeSystemText rewrites only the fixed OpenCode identity sentence (if present).
// We intentionally avoid broad keyword replacement in system prompts to prevent
// accidentally changing user-provided instructions.
func sanitizeSystemText(text string) string {
	if text == "" {
		return text
	}
	// Some clients include a fixed OpenCode identity sentence. Anthropic may treat
	// this as a non-Claude-Code fingerprint, so rewrite it to the canonical
	// Claude Code banner before generic "OpenCode"/"opencode" replacements.
	text = strings.ReplaceAll(
		text,
		"You are OpenCode, the best coding agent on the planet.",
		strings.TrimSpace(claudeCodeSystemPrompt),
	)
	return text
}

func stripCacheControlFromSystemBlocks(system any) bool {
	blocks, ok := system.([]any)
	if !ok {
		return false
	}
	changed := false
	for _, item := range blocks {
		block, ok := item.(map[string]any)
		if !ok {
			continue
		}
		if _, exists := block["cache_control"]; !exists {
			continue
		}
		delete(block, "cache_control")
		changed = true
	}
	return changed
}

func normalizeClaudeOAuthRequestBody(body []byte, modelID string, opts claudeOAuthNormalizeOptions) ([]byte, string) {
	if len(body) == 0 {
		return body, modelID
	}

	// 解析为 map[string]any 用于修改字段
	var req map[string]any
	if err := json.Unmarshal(body, &req); err != nil {
		return body, modelID
	}

	modified := false

	if system, ok := req["system"]; ok {
		switch v := system.(type) {
		case string:
			sanitized := sanitizeSystemText(v)
			if sanitized != v {
				req["system"] = sanitized
				modified = true
			}
		case []any:
			for _, item := range v {
				block, ok := item.(map[string]any)
				if !ok {
					continue
				}
				if blockType, _ := block["type"].(string); blockType != "text" {
					continue
				}
				text, ok := block["text"].(string)
				if !ok || text == "" {
					continue
				}
				sanitized := sanitizeSystemText(text)
				if sanitized != text {
					block["text"] = sanitized
					modified = true
				}
			}
		}
	}

	if rawModel, ok := req["model"].(string); ok {
		normalized := claude.NormalizeModelID(rawModel)
		if normalized != rawModel {
			req["model"] = normalized
			modelID = normalized
			modified = true
		}
	}

	// 确保 tools 字段存在（即使为空数组）
	if _, exists := req["tools"]; !exists {
		req["tools"] = []any{}
		modified = true
	}

	if opts.stripSystemCacheControl {
		if system, ok := req["system"]; ok {
			_ = stripCacheControlFromSystemBlocks(system)
			modified = true
		}
	}

	if opts.injectMetadata && opts.metadataUserID != "" {
		metadata, ok := req["metadata"].(map[string]any)
		if !ok {
			metadata = map[string]any{}
			req["metadata"] = metadata
		}
		if existing, ok := metadata["user_id"].(string); !ok || existing == "" {
			metadata["user_id"] = opts.metadataUserID
			modified = true
		}
	}

	if _, hasTemp := req["temperature"]; hasTemp {
		delete(req, "temperature")
		modified = true
	}
	if _, hasChoice := req["tool_choice"]; hasChoice {
		delete(req, "tool_choice")
		modified = true
	}

	if !modified {
		return body, modelID
	}

	newBody, err := json.Marshal(req)
	if err != nil {
		return body, modelID
	}
	return newBody, modelID
}

func (s *GatewayService) buildOAuthMetadataUserID(parsed *ParsedRequest, account *Account, fp *Fingerprint) string {
	if parsed == nil || account == nil {
		return ""
	}
	if parsed.MetadataUserID != "" {
		return ""
	}

	userID := strings.TrimSpace(account.GetClaudeUserID())
	if userID == "" && fp != nil {
		userID = fp.ClientID
	}
	if userID == "" {
		// Fall back to a random, well-formed client id so we can still satisfy
		// Claude Code OAuth requirements when account metadata is incomplete.
		userID = generateClientID()
	}

	sessionHash := s.GenerateSessionHash(parsed)
	sessionID := uuid.NewString()
	if sessionHash != "" {
		seed := fmt.Sprintf("%d::%s", account.ID, sessionHash)
		sessionID = generateSessionUUID(seed)
	}

	// Prefer the newer format that includes account_uuid (if present),
	// otherwise fall back to the legacy Claude Code format.
	accountUUID := strings.TrimSpace(account.GetExtraString("account_uuid"))
	if accountUUID != "" {
		return fmt.Sprintf("user_%s_account_%s_session_%s", userID, accountUUID, sessionID)
	}
	return fmt.Sprintf("user_%s_account__session_%s", userID, sessionID)
}

func generateSessionUUID(seed string) string {
	if seed == "" {
		return uuid.NewString()
	}
	hash := sha256.Sum256([]byte(seed))
	bytes := hash[:16]
	bytes[6] = (bytes[6] & 0x0f) | 0x40
	bytes[8] = (bytes[8] & 0x3f) | 0x80
	return fmt.Sprintf("%x-%x-%x-%x-%x",
		bytes[0:4], bytes[4:6], bytes[6:8], bytes[8:10], bytes[10:16])
}

// SelectAccount 选择账号（粘性会话+优先级）
func (s *GatewayService) SelectAccount(ctx context.Context, groupID *int64, sessionHash string) (*Account, error) {
	return s.SelectAccountForModel(ctx, groupID, sessionHash, "")
}

// SelectAccountForModel 选择支持指定模型的账号（粘性会话+优先级+模型映射）
func (s *GatewayService) SelectAccountForModel(ctx context.Context, groupID *int64, sessionHash string, requestedModel string) (*Account, error) {
	return s.SelectAccountForModelWithExclusions(ctx, groupID, sessionHash, requestedModel, nil)
}

// SelectAccountForModelWithExclusions selects an account supporting the requested model while excluding specified accounts.
func (s *GatewayService) SelectAccountForModelWithExclusions(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}) (*Account, error) {
	// 优先检查 context 中的强制平台（/antigravity 路由）
	var platform string
	forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string)
	if hasForcePlatform && forcePlatform != "" {
		platform = forcePlatform
	} else if groupID != nil {
		group, resolvedGroupID, err := s.resolveGatewayGroup(ctx, groupID)
		if err != nil {
			return nil, err
		}
		groupID = resolvedGroupID
		ctx = s.withGroupContext(ctx, group)
		platform = group.Platform
	} else {
		// 无分组时只使用原生 anthropic 平台
		platform = PlatformAnthropic
	}

	// anthropic/gemini 分组支持混合调度（包含启用了 mixed_scheduling 的 antigravity 账户）
	// 注意：强制平台模式不走混合调度
	if (platform == PlatformAnthropic || platform == PlatformGemini) && !hasForcePlatform {
		return s.selectAccountWithMixedScheduling(ctx, groupID, sessionHash, requestedModel, excludedIDs, platform)
	}

	// antigravity 分组、强制平台模式或无分组使用单平台选择
	// 注意：强制平台模式也必须遵守分组限制，不再回退到全平台查询
	return s.selectAccountForModelWithPlatform(ctx, groupID, sessionHash, requestedModel, excludedIDs, platform)
}

// SelectAccountWithLoadAwareness selects account with load-awareness and wait plan.
// metadataUserID: 已废弃参数，会话限制现在统一使用 sessionHash
func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}, metadataUserID string) (*AccountSelectionResult, error) {
	// 调试日志：记录调度入口参数
	excludedIDsList := make([]int64, 0, len(excludedIDs))
	for id := range excludedIDs {
		excludedIDsList = append(excludedIDsList, id)
	}
	slog.Debug("account_scheduling_starting",
		"group_id", derefGroupID(groupID),
		"model", requestedModel,
		"session", shortSessionHash(sessionHash),
		"excluded_ids", excludedIDsList)

	cfg := s.schedulingConfig()

	var stickyAccountID int64
	if sessionHash != "" && s.cache != nil {
		if accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash); err == nil {
			stickyAccountID = accountID
		}
	}

	// 检查 Claude Code 客户端限制（可能会替换 groupID 为降级分组）
	group, groupID, err := s.checkClaudeCodeRestriction(ctx, groupID)
	if err != nil {
		return nil, err
	}
	ctx = s.withGroupContext(ctx, group)

	if s.debugModelRoutingEnabled() && requestedModel != "" {
		groupPlatform := ""
		if group != nil {
			groupPlatform = group.Platform
		}
		log.Printf("[ModelRoutingDebug] select entry: group_id=%v group_platform=%s model=%s session=%s sticky_account=%d load_batch=%v concurrency=%v",
			derefGroupID(groupID), groupPlatform, requestedModel, shortSessionHash(sessionHash), stickyAccountID, cfg.LoadBatchEnabled, s.concurrencyService != nil)
	}

	if s.concurrencyService == nil || !cfg.LoadBatchEnabled {
		// 复制排除列表，用于会话限制拒绝时的重试
		localExcluded := make(map[int64]struct{})
		for k, v := range excludedIDs {
			localExcluded[k] = v
		}

		for {
			account, err := s.SelectAccountForModelWithExclusions(ctx, groupID, sessionHash, requestedModel, localExcluded)
			if err != nil {
				return nil, err
			}

			result, err := s.tryAcquireAccountSlot(ctx, account.ID, account.Concurrency)
			if err == nil && result.Acquired {
				// 获取槽位后检查会话限制（使用 sessionHash 作为会话标识符）
				if !s.checkAndRegisterSession(ctx, account, sessionHash) {
					result.ReleaseFunc()                   // 释放槽位
					localExcluded[account.ID] = struct{}{} // 排除此账号
					continue                               // 重新选择
				}
				return &AccountSelectionResult{
					Account:     account,
					Acquired:    true,
					ReleaseFunc: result.ReleaseFunc,
				}, nil
			}

			// 对于等待计划的情况，也需要先检查会话限制
			if !s.checkAndRegisterSession(ctx, account, sessionHash) {
				localExcluded[account.ID] = struct{}{}
				continue
			}

			if stickyAccountID > 0 && stickyAccountID == account.ID && s.concurrencyService != nil {
				waitingCount, _ := s.concurrencyService.GetAccountWaitingCount(ctx, account.ID)
				if waitingCount < cfg.StickySessionMaxWaiting {
					return &AccountSelectionResult{
						Account: account,
						WaitPlan: &AccountWaitPlan{
							AccountID:      account.ID,
							MaxConcurrency: account.Concurrency,
							Timeout:        cfg.StickySessionWaitTimeout,
							MaxWaiting:     cfg.StickySessionMaxWaiting,
						},
					}, nil
				}
			}
			return &AccountSelectionResult{
				Account: account,
				WaitPlan: &AccountWaitPlan{
					AccountID:      account.ID,
					MaxConcurrency: account.Concurrency,
					Timeout:        cfg.FallbackWaitTimeout,
					MaxWaiting:     cfg.FallbackMaxWaiting,
				},
			}, nil
		}
	}

	platform, hasForcePlatform, err := s.resolvePlatform(ctx, groupID, group)
	if err != nil {
		return nil, err
	}
	preferOAuth := platform == PlatformGemini
	if s.debugModelRoutingEnabled() && platform == PlatformAnthropic && requestedModel != "" {
		log.Printf("[ModelRoutingDebug] load-aware enabled: group_id=%v model=%s session=%s platform=%s", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), platform)
	}

	// Antigravity 模型系列检查（在账号选择前检查，确保所有代码路径都经过此检查）
	if platform == PlatformAntigravity && groupID != nil && requestedModel != "" {
		if err := s.checkAntigravityModelScope(ctx, *groupID, requestedModel); err != nil {
			return nil, err
		}
	}

	accounts, useMixed, err := s.listSchedulableAccounts(ctx, groupID, platform, hasForcePlatform)
	if err != nil {
		return nil, err
	}
	if len(accounts) == 0 {
		return nil, errors.New("no available accounts")
	}

	isExcluded := func(accountID int64) bool {
		if excludedIDs == nil {
			return false
		}
		_, excluded := excludedIDs[accountID]
		return excluded
	}

	// 提前构建 accountByID（供 Layer 1 和 Layer 1.5 使用）
	accountByID := make(map[int64]*Account, len(accounts))
	for i := range accounts {
		accountByID[accounts[i].ID] = &accounts[i]
	}

	// 获取模型路由配置（仅 anthropic 平台）
	var routingAccountIDs []int64
	if group != nil && requestedModel != "" && group.Platform == PlatformAnthropic {
		routingAccountIDs = group.GetRoutingAccountIDs(requestedModel)
		if s.debugModelRoutingEnabled() {
			log.Printf("[ModelRoutingDebug] context group routing: group_id=%d model=%s enabled=%v rules=%d matched_ids=%v session=%s sticky_account=%d",
				group.ID, requestedModel, group.ModelRoutingEnabled, len(group.ModelRouting), routingAccountIDs, shortSessionHash(sessionHash), stickyAccountID)
			if len(routingAccountIDs) == 0 && group.ModelRoutingEnabled && len(group.ModelRouting) > 0 {
				keys := make([]string, 0, len(group.ModelRouting))
				for k := range group.ModelRouting {
					keys = append(keys, k)
				}
				sort.Strings(keys)
				const maxKeys = 20
				if len(keys) > maxKeys {
					keys = keys[:maxKeys]
				}
				log.Printf("[ModelRoutingDebug] context group routing miss: group_id=%d model=%s patterns(sample)=%v", group.ID, requestedModel, keys)
			}
		}
	}

	// ============ Layer 1: 模型路由优先选择（优先级高于粘性会话） ============
	if len(routingAccountIDs) > 0 && s.concurrencyService != nil {
		// 1. 过滤出路由列表中可调度的账号
		var routingCandidates []*Account
		var filteredExcluded, filteredMissing, filteredUnsched, filteredPlatform, filteredModelScope, filteredModelMapping, filteredWindowCost int
		var modelScopeSkippedIDs []int64 // 记录因模型限流被跳过的账号 ID
		for _, routingAccountID := range routingAccountIDs {
			if isExcluded(routingAccountID) {
				filteredExcluded++
				continue
			}
			account, ok := accountByID[routingAccountID]
			if !ok || !account.IsSchedulable() {
				if !ok {
					filteredMissing++
				} else {
					filteredUnsched++
				}
				continue
			}
			if !s.isAccountAllowedForPlatform(account, platform, useMixed) {
				filteredPlatform++
				continue
			}
			if requestedModel != "" && !s.isModelSupportedByAccountWithContext(ctx, account, requestedModel) {
				filteredModelMapping++
				continue
			}
			if !account.IsSchedulableForModelWithContext(ctx, requestedModel) {
				filteredModelScope++
				modelScopeSkippedIDs = append(modelScopeSkippedIDs, account.ID)
				continue
			}
			// 窗口费用检查（非粘性会话路径）
			if !s.isAccountSchedulableForWindowCost(ctx, account, false) {
				filteredWindowCost++
				continue
			}
			routingCandidates = append(routingCandidates, account)
		}

		if s.debugModelRoutingEnabled() {
			log.Printf("[ModelRoutingDebug] routed candidates: group_id=%v model=%s routed=%d candidates=%d filtered(excluded=%d missing=%d unsched=%d platform=%d model_scope=%d model_mapping=%d window_cost=%d)",
				derefGroupID(groupID), requestedModel, len(routingAccountIDs), len(routingCandidates),
				filteredExcluded, filteredMissing, filteredUnsched, filteredPlatform, filteredModelScope, filteredModelMapping, filteredWindowCost)
			if len(modelScopeSkippedIDs) > 0 {
				log.Printf("[ModelRoutingDebug] model_rate_limited accounts skipped: group_id=%v model=%s account_ids=%v",
					derefGroupID(groupID), requestedModel, modelScopeSkippedIDs)
			}
		}

		if len(routingCandidates) > 0 {
			// 1.5. 在路由账号范围内检查粘性会话
			if sessionHash != "" && s.cache != nil {
				stickyAccountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
				if err == nil && stickyAccountID > 0 && containsInt64(routingAccountIDs, stickyAccountID) && !isExcluded(stickyAccountID) {
					// 粘性账号在路由列表中，优先使用
					if stickyAccount, ok := accountByID[stickyAccountID]; ok {
						if stickyAccount.IsSchedulable() &&
							s.isAccountAllowedForPlatform(stickyAccount, platform, useMixed) &&
							(requestedModel == "" || s.isModelSupportedByAccountWithContext(ctx, stickyAccount, requestedModel)) &&
							stickyAccount.IsSchedulableForModelWithContext(ctx, requestedModel) &&
							s.isAccountSchedulableForWindowCost(ctx, stickyAccount, true) { // 粘性会话窗口费用检查
							result, err := s.tryAcquireAccountSlot(ctx, stickyAccountID, stickyAccount.Concurrency)
							if err == nil && result.Acquired {
								// 会话数量限制检查
								if !s.checkAndRegisterSession(ctx, stickyAccount, sessionHash) {
									result.ReleaseFunc() // 释放槽位
									// 继续到负载感知选择
								} else {
									_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL)
									if s.debugModelRoutingEnabled() {
										log.Printf("[ModelRoutingDebug] routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), stickyAccountID)
									}
									return &AccountSelectionResult{
										Account:     stickyAccount,
										Acquired:    true,
										ReleaseFunc: result.ReleaseFunc,
									}, nil
								}
							}

							waitingCount, _ := s.concurrencyService.GetAccountWaitingCount(ctx, stickyAccountID)
							if waitingCount < cfg.StickySessionMaxWaiting {
								// 会话数量限制检查（等待计划也需要占用会话配额）
								if !s.checkAndRegisterSession(ctx, stickyAccount, sessionHash) {
									// 会话限制已满，继续到负载感知选择
								} else {
									return &AccountSelectionResult{
										Account: stickyAccount,
										WaitPlan: &AccountWaitPlan{
											AccountID:      stickyAccountID,
											MaxConcurrency: stickyAccount.Concurrency,
											Timeout:        cfg.StickySessionWaitTimeout,
											MaxWaiting:     cfg.StickySessionMaxWaiting,
										},
									}, nil
								}
							}
							// 粘性账号槽位满且等待队列已满，继续使用负载感知选择
						}
					} else {
						_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
					}
				}
			}

			// 2. 批量获取负载信息
			routingLoads := make([]AccountWithConcurrency, 0, len(routingCandidates))
			for _, acc := range routingCandidates {
				routingLoads = append(routingLoads, AccountWithConcurrency{
					ID:             acc.ID,
					MaxConcurrency: acc.Concurrency,
				})
			}
			routingLoadMap, _ := s.concurrencyService.GetAccountsLoadBatch(ctx, routingLoads)

			// 3. 按负载感知排序
			var routingAvailable []accountWithLoad
			for _, acc := range routingCandidates {
				loadInfo := routingLoadMap[acc.ID]
				if loadInfo == nil {
					loadInfo = &AccountLoadInfo{AccountID: acc.ID}
				}
				if loadInfo.LoadRate < 100 {
					routingAvailable = append(routingAvailable, accountWithLoad{account: acc, loadInfo: loadInfo})
				}
			}

			if len(routingAvailable) > 0 {
				// 排序：优先级 > 负载率 > 最后使用时间
				sort.SliceStable(routingAvailable, func(i, j int) bool {
					a, b := routingAvailable[i], routingAvailable[j]
					if a.account.Priority != b.account.Priority {
						return a.account.Priority < b.account.Priority
					}
					if a.loadInfo.LoadRate != b.loadInfo.LoadRate {
						return a.loadInfo.LoadRate < b.loadInfo.LoadRate
					}
					switch {
					case a.account.LastUsedAt == nil && b.account.LastUsedAt != nil:
						return true
					case a.account.LastUsedAt != nil && b.account.LastUsedAt == nil:
						return false
					case a.account.LastUsedAt == nil && b.account.LastUsedAt == nil:
						return false
					default:
						return a.account.LastUsedAt.Before(*b.account.LastUsedAt)
					}
				})

				// 4. 尝试获取槽位
				for _, item := range routingAvailable {
					result, err := s.tryAcquireAccountSlot(ctx, item.account.ID, item.account.Concurrency)
					if err == nil && result.Acquired {
						// 会话数量限制检查
						if !s.checkAndRegisterSession(ctx, item.account, sessionHash) {
							result.ReleaseFunc() // 释放槽位，继续尝试下一个账号
							continue
						}
						if sessionHash != "" && s.cache != nil {
							_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, item.account.ID, stickySessionTTL)
						}
						if s.debugModelRoutingEnabled() {
							log.Printf("[ModelRoutingDebug] routed select: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), item.account.ID)
						}
						return &AccountSelectionResult{
							Account:     item.account,
							Acquired:    true,
							ReleaseFunc: result.ReleaseFunc,
						}, nil
					}
				}

				// 5. 所有路由账号槽位满，尝试返回等待计划（选择负载最低的）
				// 遍历找到第一个满足会话限制的账号
				for _, item := range routingAvailable {
					if !s.checkAndRegisterSession(ctx, item.account, sessionHash) {
						continue // 会话限制已满，尝试下一个
					}
					if s.debugModelRoutingEnabled() {
						log.Printf("[ModelRoutingDebug] routed wait: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), item.account.ID)
					}
					return &AccountSelectionResult{
						Account: item.account,
						WaitPlan: &AccountWaitPlan{
							AccountID:      item.account.ID,
							MaxConcurrency: item.account.Concurrency,
							Timeout:        cfg.StickySessionWaitTimeout,
							MaxWaiting:     cfg.StickySessionMaxWaiting,
						},
					}, nil
				}
				// 所有路由账号会话限制都已满，继续到 Layer 2 回退
			}
			// 路由列表中的账号都不可用（负载率 >= 100），继续到 Layer 2 回退
			log.Printf("[ModelRouting] All routed accounts unavailable for model=%s, falling back to normal selection", requestedModel)
		}
	}

	// ============ Layer 1.5: 粘性会话（仅在无模型路由配置时生效） ============
	if len(routingAccountIDs) == 0 && sessionHash != "" && s.cache != nil {
		accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
		if err == nil && accountID > 0 && !isExcluded(accountID) {
			account, ok := accountByID[accountID]
			if ok {
				// 检查账户是否需要清理粘性会话绑定
				// Check if the account needs sticky session cleanup
				clearSticky := shouldClearStickySession(account, requestedModel)
				if clearSticky {
					_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
				}
				if !clearSticky && s.isAccountInGroup(account, groupID) &&
					s.isAccountAllowedForPlatform(account, platform, useMixed) &&
					(requestedModel == "" || s.isModelSupportedByAccountWithContext(ctx, account, requestedModel)) &&
					account.IsSchedulableForModelWithContext(ctx, requestedModel) &&
					s.isAccountSchedulableForWindowCost(ctx, account, true) { // 粘性会话窗口费用检查
					result, err := s.tryAcquireAccountSlot(ctx, accountID, account.Concurrency)
					if err == nil && result.Acquired {
						// 会话数量限制检查
						// Session count limit check
						if !s.checkAndRegisterSession(ctx, account, sessionHash) {
							result.ReleaseFunc() // 释放槽位，继续到 Layer 2
						} else {
							_ = s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL)
							return &AccountSelectionResult{
								Account:     account,
								Acquired:    true,
								ReleaseFunc: result.ReleaseFunc,
							}, nil
						}
					}

					waitingCount, _ := s.concurrencyService.GetAccountWaitingCount(ctx, accountID)
					if waitingCount < cfg.StickySessionMaxWaiting {
						// 会话数量限制检查（等待计划也需要占用会话配额）
						// Session count limit check (wait plan also requires session quota)
						if !s.checkAndRegisterSession(ctx, account, sessionHash) {
							// 会话限制已满，继续到 Layer 2
							// Session limit full, continue to Layer 2
						} else {
							return &AccountSelectionResult{
								Account: account,
								WaitPlan: &AccountWaitPlan{
									AccountID:      accountID,
									MaxConcurrency: account.Concurrency,
									Timeout:        cfg.StickySessionWaitTimeout,
									MaxWaiting:     cfg.StickySessionMaxWaiting,
								},
							}, nil
						}
					}
				}
			}
		}
	}

	// ============ Layer 2: 负载感知选择 ============
	candidates := make([]*Account, 0, len(accounts))
	for i := range accounts {
		acc := &accounts[i]
		if isExcluded(acc.ID) {
			continue
		}
		// Scheduler snapshots can be temporarily stale (bucket rebuild is throttled);
		// re-check schedulability here so recently rate-limited/overloaded accounts
		// are not selected again before the bucket is rebuilt.
		if !acc.IsSchedulable() {
			continue
		}
		if !s.isAccountAllowedForPlatform(acc, platform, useMixed) {
			continue
		}
		if requestedModel != "" && !s.isModelSupportedByAccountWithContext(ctx, acc, requestedModel) {
			continue
		}
		if !acc.IsSchedulableForModelWithContext(ctx, requestedModel) {
			continue
		}
		// 窗口费用检查（非粘性会话路径）
		if !s.isAccountSchedulableForWindowCost(ctx, acc, false) {
			continue
		}
		candidates = append(candidates, acc)
	}

	if len(candidates) == 0 {
		return nil, errors.New("no available accounts")
	}

	accountLoads := make([]AccountWithConcurrency, 0, len(candidates))
	for _, acc := range candidates {
		accountLoads = append(accountLoads, AccountWithConcurrency{
			ID:             acc.ID,
			MaxConcurrency: acc.Concurrency,
		})
	}

	loadMap, err := s.concurrencyService.GetAccountsLoadBatch(ctx, accountLoads)
	if err != nil {
		if result, ok := s.tryAcquireByLegacyOrder(ctx, candidates, groupID, sessionHash, preferOAuth); ok {
			return result, nil
		}
	} else {
		// Antigravity 平台：获取模型负载信息
		var modelLoadMap map[int64]*ModelLoadInfo
		isAntigravity := platform == PlatformAntigravity

		var available []accountWithLoad
		for _, acc := range candidates {
			loadInfo := loadMap[acc.ID]
			if loadInfo == nil {
				loadInfo = &AccountLoadInfo{AccountID: acc.ID}
			}
			if loadInfo.LoadRate < 100 {
				available = append(available, accountWithLoad{
					account:  acc,
					loadInfo: loadInfo,
				})
			}
		}

		// Antigravity 平台：按账号实际映射后的模型名获取模型负载（与 Forward 的统计保持一致）
		if isAntigravity && requestedModel != "" && s.cache != nil && len(available) > 0 {
			modelLoadMap = make(map[int64]*ModelLoadInfo, len(available))
			modelToAccountIDs := make(map[string][]int64)
			for _, item := range available {
				mappedModel := mapAntigravityModel(item.account, requestedModel)
				if mappedModel == "" {
					continue
				}
				modelToAccountIDs[mappedModel] = append(modelToAccountIDs[mappedModel], item.account.ID)
			}
			for model, ids := range modelToAccountIDs {
				batch, err := s.cache.GetModelLoadBatch(ctx, ids, model)
				if err != nil {
					continue
				}
				for id, info := range batch {
					modelLoadMap[id] = info
				}
			}
			if len(modelLoadMap) == 0 {
				modelLoadMap = nil
			}
		}

		// Antigravity 平台：优先级硬过滤 →（同优先级内）按调用次数选择（最少优先，新账号用平均值）
		// 其他平台：分层过滤选择：优先级 → 负载率 → LRU
		if isAntigravity {
			for len(available) > 0 {
				// 1. 取优先级最小的集合（硬过滤）
				candidates := filterByMinPriority(available)
				// 2. 同优先级内按调用次数选择（调用次数最少优先，新账号使用平均值）
				selected := selectByCallCount(candidates, modelLoadMap, preferOAuth)
				if selected == nil {
					break
				}

				result, err := s.tryAcquireAccountSlot(ctx, selected.account.ID, selected.account.Concurrency)
				if err == nil && result.Acquired {
					// 会话数量限制检查
					if !s.checkAndRegisterSession(ctx, selected.account, sessionHash) {
						result.ReleaseFunc() // 释放槽位，继续尝试下一个账号
					} else {
						if sessionHash != "" && s.cache != nil {
							_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, selected.account.ID, stickySessionTTL)
						}
						return &AccountSelectionResult{
							Account:     selected.account,
							Acquired:    true,
							ReleaseFunc: result.ReleaseFunc,
						}, nil
					}
				}

				// 移除已尝试的账号，重新选择
				selectedID := selected.account.ID
				newAvailable := make([]accountWithLoad, 0, len(available)-1)
				for _, acc := range available {
					if acc.account.ID != selectedID {
						newAvailable = append(newAvailable, acc)
					}
				}
				available = newAvailable
			}
		} else {
			for len(available) > 0 {
				// 1. 取优先级最小的集合
				candidates := filterByMinPriority(available)
				// 2. 取负载率最低的集合
				candidates = filterByMinLoadRate(candidates)
				// 3. LRU 选择最久未用的账号
				selected := selectByLRU(candidates, preferOAuth)
				if selected == nil {
					break
				}

				result, err := s.tryAcquireAccountSlot(ctx, selected.account.ID, selected.account.Concurrency)
				if err == nil && result.Acquired {
					// 会话数量限制检查
					if !s.checkAndRegisterSession(ctx, selected.account, sessionHash) {
						result.ReleaseFunc() // 释放槽位，继续尝试下一个账号
					} else {
						if sessionHash != "" && s.cache != nil {
							_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, selected.account.ID, stickySessionTTL)
						}
						return &AccountSelectionResult{
							Account:     selected.account,
							Acquired:    true,
							ReleaseFunc: result.ReleaseFunc,
						}, nil
					}
				}

				// 移除已尝试的账号，重新进行分层过滤
				selectedID := selected.account.ID
				newAvailable := make([]accountWithLoad, 0, len(available)-1)
				for _, acc := range available {
					if acc.account.ID != selectedID {
						newAvailable = append(newAvailable, acc)
					}
				}
				available = newAvailable
			}
		}
	}

	// ============ Layer 3: 兜底排队 ============
	s.sortCandidatesForFallback(candidates, preferOAuth, cfg.FallbackSelectionMode)
	for _, acc := range candidates {
		// 会话数量限制检查（等待计划也需要占用会话配额）
		if !s.checkAndRegisterSession(ctx, acc, sessionHash) {
			continue // 会话限制已满，尝试下一个账号
		}
		return &AccountSelectionResult{
			Account: acc,
			WaitPlan: &AccountWaitPlan{
				AccountID:      acc.ID,
				MaxConcurrency: acc.Concurrency,
				Timeout:        cfg.FallbackWaitTimeout,
				MaxWaiting:     cfg.FallbackMaxWaiting,
			},
		}, nil
	}
	return nil, errors.New("no available accounts")
}

func (s *GatewayService) tryAcquireByLegacyOrder(ctx context.Context, candidates []*Account, groupID *int64, sessionHash string, preferOAuth bool) (*AccountSelectionResult, bool) {
	ordered := append([]*Account(nil), candidates...)
	sortAccountsByPriorityAndLastUsed(ordered, preferOAuth)

	for _, acc := range ordered {
		result, err := s.tryAcquireAccountSlot(ctx, acc.ID, acc.Concurrency)
		if err == nil && result.Acquired {
			// 会话数量限制检查
			if !s.checkAndRegisterSession(ctx, acc, sessionHash) {
				result.ReleaseFunc() // 释放槽位，继续尝试下一个账号
				continue
			}
			if sessionHash != "" && s.cache != nil {
				_ = s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, acc.ID, stickySessionTTL)
			}
			return &AccountSelectionResult{
				Account:     acc,
				Acquired:    true,
				ReleaseFunc: result.ReleaseFunc,
			}, true
		}
	}

	return nil, false
}

func (s *GatewayService) schedulingConfig() config.GatewaySchedulingConfig {
	if s.cfg != nil {
		return s.cfg.Gateway.Scheduling
	}
	return config.GatewaySchedulingConfig{
		StickySessionMaxWaiting:  3,
		StickySessionWaitTimeout: 45 * time.Second,
		FallbackWaitTimeout:      30 * time.Second,
		FallbackMaxWaiting:       100,
		LoadBatchEnabled:         true,
		SlotCleanupInterval:      30 * time.Second,
	}
}

func (s *GatewayService) withGroupContext(ctx context.Context, group *Group) context.Context {
	if !IsGroupContextValid(group) {
		return ctx
	}
	if existing, ok := ctx.Value(ctxkey.Group).(*Group); ok && existing != nil && existing.ID == group.ID && IsGroupContextValid(existing) {
		return ctx
	}
	return context.WithValue(ctx, ctxkey.Group, group)
}

func (s *GatewayService) groupFromContext(ctx context.Context, groupID int64) *Group {
	if group, ok := ctx.Value(ctxkey.Group).(*Group); ok && IsGroupContextValid(group) && group.ID == groupID {
		return group
	}
	return nil
}

func (s *GatewayService) resolveGroupByID(ctx context.Context, groupID int64) (*Group, error) {
	if group := s.groupFromContext(ctx, groupID); group != nil {
		return group, nil
	}
	group, err := s.groupRepo.GetByIDLite(ctx, groupID)
	if err != nil {
		return nil, fmt.Errorf("get group failed: %w", err)
	}
	return group, nil
}

func (s *GatewayService) ResolveGroupByID(ctx context.Context, groupID int64) (*Group, error) {
	return s.resolveGroupByID(ctx, groupID)
}

func (s *GatewayService) routingAccountIDsForRequest(ctx context.Context, groupID *int64, requestedModel string, platform string) []int64 {
	if groupID == nil || requestedModel == "" || platform != PlatformAnthropic {
		return nil
	}
	group, err := s.resolveGroupByID(ctx, *groupID)
	if err != nil || group == nil {
		if s.debugModelRoutingEnabled() {
			log.Printf("[ModelRoutingDebug] resolve group failed: group_id=%v model=%s platform=%s err=%v", derefGroupID(groupID), requestedModel, platform, err)
		}
		return nil
	}
	// Preserve existing behavior: model routing only applies to anthropic groups.
	if group.Platform != PlatformAnthropic {
		if s.debugModelRoutingEnabled() {
			log.Printf("[ModelRoutingDebug] skip: non-anthropic group platform: group_id=%d group_platform=%s model=%s", group.ID, group.Platform, requestedModel)
		}
		return nil
	}
	ids := group.GetRoutingAccountIDs(requestedModel)
	if s.debugModelRoutingEnabled() {
		log.Printf("[ModelRoutingDebug] routing lookup: group_id=%d model=%s enabled=%v rules=%d matched_ids=%v",
			group.ID, requestedModel, group.ModelRoutingEnabled, len(group.ModelRouting), ids)
	}
	return ids
}

func (s *GatewayService) resolveGatewayGroup(ctx context.Context, groupID *int64) (*Group, *int64, error) {
	if groupID == nil {
		return nil, nil, nil
	}

	currentID := *groupID
	visited := map[int64]struct{}{}
	for {
		if _, seen := visited[currentID]; seen {
			return nil, nil, fmt.Errorf("fallback group cycle detected")
		}
		visited[currentID] = struct{}{}

		group, err := s.resolveGroupByID(ctx, currentID)
		if err != nil {
			return nil, nil, err
		}

		if !group.ClaudeCodeOnly || IsClaudeCodeClient(ctx) {
			return group, &currentID, nil
		}

		if group.FallbackGroupID == nil {
			return nil, nil, ErrClaudeCodeOnly
		}
		currentID = *group.FallbackGroupID
	}
}

// checkClaudeCodeRestriction 检查分组的 Claude Code 客户端限制
// 如果分组启用了 claude_code_only 且请求不是来自 Claude Code 客户端：
//   - 有降级分组：返回降级分组的 ID
//   - 无降级分组：返回 ErrClaudeCodeOnly 错误
func (s *GatewayService) checkClaudeCodeRestriction(ctx context.Context, groupID *int64) (*Group, *int64, error) {
	if groupID == nil {
		return nil, groupID, nil
	}

	// 强制平台模式不检查 Claude Code 限制
	if forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string); hasForcePlatform && forcePlatform != "" {
		return nil, groupID, nil
	}

	group, resolvedID, err := s.resolveGatewayGroup(ctx, groupID)
	if err != nil {
		return nil, nil, err
	}

	return group, resolvedID, nil
}

func (s *GatewayService) resolvePlatform(ctx context.Context, groupID *int64, group *Group) (string, bool, error) {
	forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string)
	if hasForcePlatform && forcePlatform != "" {
		return forcePlatform, true, nil
	}
	if group != nil {
		return group.Platform, false, nil
	}
	if groupID != nil {
		group, err := s.resolveGroupByID(ctx, *groupID)
		if err != nil {
			return "", false, err
		}
		return group.Platform, false, nil
	}
	return PlatformAnthropic, false, nil
}

func (s *GatewayService) listSchedulableAccounts(ctx context.Context, groupID *int64, platform string, hasForcePlatform bool) ([]Account, bool, error) {
	if s.schedulerSnapshot != nil {
		accounts, useMixed, err := s.schedulerSnapshot.ListSchedulableAccounts(ctx, groupID, platform, hasForcePlatform)
		if err == nil {
			slog.Debug("account_scheduling_list_snapshot",
				"group_id", derefGroupID(groupID),
				"platform", platform,
				"use_mixed", useMixed,
				"count", len(accounts))
			for _, acc := range accounts {
				slog.Debug("account_scheduling_account_detail",
					"account_id", acc.ID,
					"name", acc.Name,
					"platform", acc.Platform,
					"type", acc.Type,
					"status", acc.Status,
					"tls_fingerprint", acc.IsTLSFingerprintEnabled())
			}
		}
		return accounts, useMixed, err
	}
	useMixed := (platform == PlatformAnthropic || platform == PlatformGemini) && !hasForcePlatform
	if useMixed {
		platforms := []string{platform, PlatformAntigravity}
		var accounts []Account
		var err error
		if groupID != nil {
			accounts, err = s.accountRepo.ListSchedulableByGroupIDAndPlatforms(ctx, *groupID, platforms)
		} else {
			accounts, err = s.accountRepo.ListSchedulableByPlatforms(ctx, platforms)
		}
		if err != nil {
			slog.Debug("account_scheduling_list_failed",
				"group_id", derefGroupID(groupID),
				"platform", platform,
				"error", err)
			return nil, useMixed, err
		}
		filtered := make([]Account, 0, len(accounts))
		for _, acc := range accounts {
			if acc.Platform == PlatformAntigravity && !acc.IsMixedSchedulingEnabled() {
				continue
			}
			filtered = append(filtered, acc)
		}
		slog.Debug("account_scheduling_list_mixed",
			"group_id", derefGroupID(groupID),
			"platform", platform,
			"raw_count", len(accounts),
			"filtered_count", len(filtered))
		for _, acc := range filtered {
			slog.Debug("account_scheduling_account_detail",
				"account_id", acc.ID,
				"name", acc.Name,
				"platform", acc.Platform,
				"type", acc.Type,
				"status", acc.Status,
				"tls_fingerprint", acc.IsTLSFingerprintEnabled())
		}
		return filtered, useMixed, nil
	}

	var accounts []Account
	var err error
	if s.cfg != nil && s.cfg.RunMode == config.RunModeSimple {
		accounts, err = s.accountRepo.ListSchedulableByPlatform(ctx, platform)
	} else if groupID != nil {
		accounts, err = s.accountRepo.ListSchedulableByGroupIDAndPlatform(ctx, *groupID, platform)
		// 分组内无账号则返回空列表，由上层处理错误，不再回退到全平台查询
	} else {
		accounts, err = s.accountRepo.ListSchedulableByPlatform(ctx, platform)
	}
	if err != nil {
		slog.Debug("account_scheduling_list_failed",
			"group_id", derefGroupID(groupID),
			"platform", platform,
			"error", err)
		return nil, useMixed, err
	}
	slog.Debug("account_scheduling_list_single",
		"group_id", derefGroupID(groupID),
		"platform", platform,
		"count", len(accounts))
	for _, acc := range accounts {
		slog.Debug("account_scheduling_account_detail",
			"account_id", acc.ID,
			"name", acc.Name,
			"platform", acc.Platform,
			"type", acc.Type,
			"status", acc.Status,
			"tls_fingerprint", acc.IsTLSFingerprintEnabled())
	}
	return accounts, useMixed, nil
}

func (s *GatewayService) isAccountAllowedForPlatform(account *Account, platform string, useMixed bool) bool {
	if account == nil {
		return false
	}
	if useMixed {
		if account.Platform == platform {
			return true
		}
		return account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()
	}
	return account.Platform == platform
}

// isAccountInGroup checks if the account belongs to the specified group.
// Returns true if groupID is nil (no group restriction) or account belongs to the group.
func (s *GatewayService) isAccountInGroup(account *Account, groupID *int64) bool {
	if groupID == nil {
		return true // 无分组限制
	}
	if account == nil {
		return false
	}
	for _, ag := range account.AccountGroups {
		if ag.GroupID == *groupID {
			return true
		}
	}
	return false
}

func (s *GatewayService) tryAcquireAccountSlot(ctx context.Context, accountID int64, maxConcurrency int) (*AcquireResult, error) {
	if s.concurrencyService == nil {
		return &AcquireResult{Acquired: true, ReleaseFunc: func() {}}, nil
	}
	return s.concurrencyService.AcquireAccountSlot(ctx, accountID, maxConcurrency)
}

// isAccountSchedulableForWindowCost 检查账号是否可根据窗口费用进行调度
// 仅适用于 Anthropic OAuth/SetupToken 账号
// 返回 true 表示可调度，false 表示不可调度
func (s *GatewayService) isAccountSchedulableForWindowCost(ctx context.Context, account *Account, isSticky bool) bool {
	// 只检查 Anthropic OAuth/SetupToken 账号
	if !account.IsAnthropicOAuthOrSetupToken() {
		return true
	}

	limit := account.GetWindowCostLimit()
	if limit <= 0 {
		return true // 未启用窗口费用限制
	}

	// 尝试从缓存获取窗口费用
	var currentCost float64
	if s.sessionLimitCache != nil {
		if cost, hit, err := s.sessionLimitCache.GetWindowCost(ctx, account.ID); err == nil && hit {
			currentCost = cost
			goto checkSchedulability
		}
	}

	// 缓存未命中，从数据库查询
	{
		// 使用统一的窗口开始时间计算逻辑（考虑窗口过期情况）
		startTime := account.GetCurrentWindowStartTime()

		stats, err := s.usageLogRepo.GetAccountWindowStats(ctx, account.ID, startTime)
		if err != nil {
			// 失败开放：查询失败时允许调度
			return true
		}

		// 使用标准费用（不含账号倍率）
		currentCost = stats.StandardCost

		// 设置缓存（忽略错误）
		if s.sessionLimitCache != nil {
			_ = s.sessionLimitCache.SetWindowCost(ctx, account.ID, currentCost)
		}
	}

checkSchedulability:
	schedulability := account.CheckWindowCostSchedulability(currentCost)

	switch schedulability {
	case WindowCostSchedulable:
		return true
	case WindowCostStickyOnly:
		return isSticky
	case WindowCostNotSchedulable:
		return false
	}
	return true
}

// checkAndRegisterSession 检查并注册会话，用于会话数量限制
// 仅适用于 Anthropic OAuth/SetupToken 账号
// sessionID: 会话标识符（使用粘性会话的 hash）
// 返回 true 表示允许（在限制内或会话已存在），false 表示拒绝（超出限制且是新会话）
func (s *GatewayService) checkAndRegisterSession(ctx context.Context, account *Account, sessionID string) bool {
	// 只检查 Anthropic OAuth/SetupToken 账号
	if !account.IsAnthropicOAuthOrSetupToken() {
		return true
	}

	maxSessions := account.GetMaxSessions()
	if maxSessions <= 0 || sessionID == "" {
		return true // 未启用会话限制或无会话ID
	}

	if s.sessionLimitCache == nil {
		return true // 缓存不可用时允许通过
	}

	idleTimeout := time.Duration(account.GetSessionIdleTimeoutMinutes()) * time.Minute

	allowed, err := s.sessionLimitCache.RegisterSession(ctx, account.ID, sessionID, maxSessions, idleTimeout)
	if err != nil {
		// 失败开放：缓存错误时允许通过
		return true
	}
	return allowed
}

func (s *GatewayService) getSchedulableAccount(ctx context.Context, accountID int64) (*Account, error) {
	if s.schedulerSnapshot != nil {
		return s.schedulerSnapshot.GetAccount(ctx, accountID)
	}
	return s.accountRepo.GetByID(ctx, accountID)
}

// filterByMinPriority 过滤出优先级最小的账号集合
func filterByMinPriority(accounts []accountWithLoad) []accountWithLoad {
	if len(accounts) == 0 {
		return accounts
	}
	minPriority := accounts[0].account.Priority
	for _, acc := range accounts[1:] {
		if acc.account.Priority < minPriority {
			minPriority = acc.account.Priority
		}
	}
	result := make([]accountWithLoad, 0, len(accounts))
	for _, acc := range accounts {
		if acc.account.Priority == minPriority {
			result = append(result, acc)
		}
	}
	return result
}

// filterByMinLoadRate 过滤出负载率最低的账号集合
func filterByMinLoadRate(accounts []accountWithLoad) []accountWithLoad {
	if len(accounts) == 0 {
		return accounts
	}
	minLoadRate := accounts[0].loadInfo.LoadRate
	for _, acc := range accounts[1:] {
		if acc.loadInfo.LoadRate < minLoadRate {
			minLoadRate = acc.loadInfo.LoadRate
		}
	}
	result := make([]accountWithLoad, 0, len(accounts))
	for _, acc := range accounts {
		if acc.loadInfo.LoadRate == minLoadRate {
			result = append(result, acc)
		}
	}
	return result
}

// selectByLRU 从集合中选择最久未用的账号
// 如果有多个账号具有相同的最小 LastUsedAt，则随机选择一个
func selectByLRU(accounts []accountWithLoad, preferOAuth bool) *accountWithLoad {
	if len(accounts) == 0 {
		return nil
	}
	if len(accounts) == 1 {
		return &accounts[0]
	}

	// 1. 找到最小的 LastUsedAt（nil 被视为最小）
	var minTime *time.Time
	hasNil := false
	for _, acc := range accounts {
		if acc.account.LastUsedAt == nil {
			hasNil = true
			break
		}
		if minTime == nil || acc.account.LastUsedAt.Before(*minTime) {
			minTime = acc.account.LastUsedAt
		}
	}

	// 2. 收集所有具有最小 LastUsedAt 的账号索引
	var candidateIdxs []int
	for i, acc := range accounts {
		if hasNil {
			if acc.account.LastUsedAt == nil {
				candidateIdxs = append(candidateIdxs, i)
			}
		} else {
			if acc.account.LastUsedAt != nil && acc.account.LastUsedAt.Equal(*minTime) {
				candidateIdxs = append(candidateIdxs, i)
			}
		}
	}

	// 3. 如果只有一个候选，直接返回
	if len(candidateIdxs) == 1 {
		return &accounts[candidateIdxs[0]]
	}

	// 4. 如果有多个候选且 preferOAuth，优先选择 OAuth 类型
	if preferOAuth {
		var oauthIdxs []int
		for _, idx := range candidateIdxs {
			if accounts[idx].account.Type == AccountTypeOAuth {
				oauthIdxs = append(oauthIdxs, idx)
			}
		}
		if len(oauthIdxs) > 0 {
			candidateIdxs = oauthIdxs
		}
	}

	// 5. 随机选择一个
	selectedIdx := candidateIdxs[mathrand.Intn(len(candidateIdxs))]
	return &accounts[selectedIdx]
}

func sortAccountsByPriorityAndLastUsed(accounts []*Account, preferOAuth bool) {
	sort.SliceStable(accounts, func(i, j int) bool {
		a, b := accounts[i], accounts[j]
		if a.Priority != b.Priority {
			return a.Priority < b.Priority
		}
		switch {
		case a.LastUsedAt == nil && b.LastUsedAt != nil:
			return true
		case a.LastUsedAt != nil && b.LastUsedAt == nil:
			return false
		case a.LastUsedAt == nil && b.LastUsedAt == nil:
			if preferOAuth && a.Type != b.Type {
				return a.Type == AccountTypeOAuth
			}
			return false
		default:
			return a.LastUsedAt.Before(*b.LastUsedAt)
		}
	})
}

// selectByCallCount 从候选账号中选择调用次数最少的账号（Antigravity 专用）
// 新账号（CallCount=0）使用平均调用次数作为虚拟值，避免冷启动被猛调
// 如果有多个账号具有相同的最小调用次数，则随机选择一个
func selectByCallCount(accounts []accountWithLoad, modelLoadMap map[int64]*ModelLoadInfo, preferOAuth bool) *accountWithLoad {
	if len(accounts) == 0 {
		return nil
	}
	if len(accounts) == 1 {
		return &accounts[0]
	}

	// 如果没有负载信息，回退到 LRU
	if modelLoadMap == nil {
		return selectByLRU(accounts, preferOAuth)
	}

	// 1. 计算平均调用次数（用于新账号冷启动）
	var totalCallCount int64
	var countWithCalls int
	for _, acc := range accounts {
		if info := modelLoadMap[acc.account.ID]; info != nil && info.CallCount > 0 {
			totalCallCount += info.CallCount
			countWithCalls++
		}
	}

	var avgCallCount int64
	if countWithCalls > 0 {
		avgCallCount = totalCallCount / int64(countWithCalls)
	}

	// 2. 获取每个账号的有效调用次数
	getEffectiveCallCount := func(acc accountWithLoad) int64 {
		if acc.account == nil {
			return 0
		}
		info := modelLoadMap[acc.account.ID]
		if info == nil || info.CallCount == 0 {
			return avgCallCount // 新账号使用平均值
		}
		return info.CallCount
	}

	// 3. 找到最小调用次数
	minCount := getEffectiveCallCount(accounts[0])
	for _, acc := range accounts[1:] {
		if c := getEffectiveCallCount(acc); c < minCount {
			minCount = c
		}
	}

	// 4. 收集所有具有最小调用次数的账号
	var candidateIdxs []int
	for i, acc := range accounts {
		if getEffectiveCallCount(acc) == minCount {
			candidateIdxs = append(candidateIdxs, i)
		}
	}

	// 5. 如果只有一个候选，直接返回
	if len(candidateIdxs) == 1 {
		return &accounts[candidateIdxs[0]]
	}

	// 6. preferOAuth 处理
	if preferOAuth {
		var oauthIdxs []int
		for _, idx := range candidateIdxs {
			if accounts[idx].account.Type == AccountTypeOAuth {
				oauthIdxs = append(oauthIdxs, idx)
			}
		}
		if len(oauthIdxs) > 0 {
			candidateIdxs = oauthIdxs
		}
	}

	// 7. 随机选择
	return &accounts[candidateIdxs[mathrand.Intn(len(candidateIdxs))]]
}

// sortCandidatesForFallback 根据配置选择排序策略
// mode: "last_used"(按最后使用时间) 或 "random"(随机)
func (s *GatewayService) sortCandidatesForFallback(accounts []*Account, preferOAuth bool, mode string) {
	if mode == "random" {
		// 先按优先级排序，然后在同优先级内随机打乱
		sortAccountsByPriorityOnly(accounts, preferOAuth)
		shuffleWithinPriority(accounts)
	} else {
		// 默认按最后使用时间排序
		sortAccountsByPriorityAndLastUsed(accounts, preferOAuth)
	}
}

// sortAccountsByPriorityOnly 仅按优先级排序
func sortAccountsByPriorityOnly(accounts []*Account, preferOAuth bool) {
	sort.SliceStable(accounts, func(i, j int) bool {
		a, b := accounts[i], accounts[j]
		if a.Priority != b.Priority {
			return a.Priority < b.Priority
		}
		if preferOAuth && a.Type != b.Type {
			return a.Type == AccountTypeOAuth
		}
		return false
	})
}

// shuffleWithinPriority 在同优先级内随机打乱顺序
func shuffleWithinPriority(accounts []*Account) {
	if len(accounts) <= 1 {
		return
	}
	r := mathrand.New(mathrand.NewSource(time.Now().UnixNano()))
	start := 0
	for start < len(accounts) {
		priority := accounts[start].Priority
		end := start + 1
		for end < len(accounts) && accounts[end].Priority == priority {
			end++
		}
		// 对 [start, end) 范围内的账户随机打乱
		if end-start > 1 {
			r.Shuffle(end-start, func(i, j int) {
				accounts[start+i], accounts[start+j] = accounts[start+j], accounts[start+i]
			})
		}
		start = end
	}
}

// selectAccountForModelWithPlatform 选择单平台账户（完全隔离）
func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}, platform string) (*Account, error) {
	// 对 Antigravity 平台，检查请求的模型系列是否在分组支持范围内
	if platform == PlatformAntigravity && groupID != nil && requestedModel != "" {
		if err := s.checkAntigravityModelScope(ctx, *groupID, requestedModel); err != nil {
			return nil, err
		}
	}

	preferOAuth := platform == PlatformGemini
	routingAccountIDs := s.routingAccountIDsForRequest(ctx, groupID, requestedModel, platform)

	var accounts []Account
	accountsLoaded := false

	// ============ Model Routing (legacy path): apply before sticky session ============
	// When load-awareness is disabled (e.g. concurrency service not configured), we still honor model routing
	// so switching model can switch upstream account within the same sticky session.
	if len(routingAccountIDs) > 0 {
		if s.debugModelRoutingEnabled() {
			log.Printf("[ModelRoutingDebug] legacy routed begin: group_id=%v model=%s platform=%s session=%s routed_ids=%v",
				derefGroupID(groupID), requestedModel, platform, shortSessionHash(sessionHash), routingAccountIDs)
		}
		// 1) Sticky session only applies if the bound account is within the routing set.
		if sessionHash != "" && s.cache != nil {
			accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
			if err == nil && accountID > 0 && containsInt64(routingAccountIDs, accountID) {
				if _, excluded := excludedIDs[accountID]; !excluded {
					account, err := s.getSchedulableAccount(ctx, accountID)
					// 检查账号分组归属和平台匹配（确保粘性会话不会跨分组或跨平台）
					if err == nil {
						clearSticky := shouldClearStickySession(account, requestedModel)
						if clearSticky {
							_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
						}
						if !clearSticky && s.isAccountInGroup(account, groupID) && account.Platform == platform && (requestedModel == "" || s.isModelSupportedByAccountWithContext(ctx, account, requestedModel)) && account.IsSchedulableForModelWithContext(ctx, requestedModel) {
							if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
								log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
							}
							if s.debugModelRoutingEnabled() {
								log.Printf("[ModelRoutingDebug] legacy routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), accountID)
							}
							return account, nil
						}
					}
				}
			}
		}

		// 2) Select an account from the routed candidates.
		forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string)
		if hasForcePlatform && forcePlatform == "" {
			hasForcePlatform = false
		}
		var err error
		accounts, _, err = s.listSchedulableAccounts(ctx, groupID, platform, hasForcePlatform)
		if err != nil {
			return nil, fmt.Errorf("query accounts failed: %w", err)
		}
		accountsLoaded = true

		routingSet := make(map[int64]struct{}, len(routingAccountIDs))
		for _, id := range routingAccountIDs {
			if id > 0 {
				routingSet[id] = struct{}{}
			}
		}

		var selected *Account
		for i := range accounts {
			acc := &accounts[i]
			if _, ok := routingSet[acc.ID]; !ok {
				continue
			}
			if _, excluded := excludedIDs[acc.ID]; excluded {
				continue
			}
			// Scheduler snapshots can be temporarily stale; re-check schedulability here to
			// avoid selecting accounts that were recently rate-limited/overloaded.
			if !acc.IsSchedulable() {
				continue
			}
			if requestedModel != "" && !s.isModelSupportedByAccountWithContext(ctx, acc, requestedModel) {
				continue
			}
			if !acc.IsSchedulableForModelWithContext(ctx, requestedModel) {
				continue
			}
			if selected == nil {
				selected = acc
				continue
			}
			if acc.Priority < selected.Priority {
				selected = acc
			} else if acc.Priority == selected.Priority {
				switch {
				case acc.LastUsedAt == nil && selected.LastUsedAt != nil:
					selected = acc
				case acc.LastUsedAt != nil && selected.LastUsedAt == nil:
					// keep selected (never used is preferred)
				case acc.LastUsedAt == nil && selected.LastUsedAt == nil:
					if preferOAuth && acc.Type != selected.Type && acc.Type == AccountTypeOAuth {
						selected = acc
					}
				default:
					if acc.LastUsedAt.Before(*selected.LastUsedAt) {
						selected = acc
					}
				}
			}
		}

		if selected != nil {
			if sessionHash != "" && s.cache != nil {
				if err := s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, selected.ID, stickySessionTTL); err != nil {
					log.Printf("set session account failed: session=%s account_id=%d err=%v", sessionHash, selected.ID, err)
				}
			}
			if s.debugModelRoutingEnabled() {
				log.Printf("[ModelRoutingDebug] legacy routed select: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), selected.ID)
			}
			return selected, nil
		}
		log.Printf("[ModelRouting] No routed accounts available for model=%s, falling back to normal selection", requestedModel)
	}

	// 1. 查询粘性会话
	if sessionHash != "" && s.cache != nil {
		accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
		if err == nil && accountID > 0 {
			if _, excluded := excludedIDs[accountID]; !excluded {
				account, err := s.getSchedulableAccount(ctx, accountID)
				// 检查账号分组归属和平台匹配（确保粘性会话不会跨分组或跨平台）
				if err == nil {
					clearSticky := shouldClearStickySession(account, requestedModel)
					if clearSticky {
						_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
					}
					if !clearSticky && s.isAccountInGroup(account, groupID) && account.Platform == platform && (requestedModel == "" || s.isModelSupportedByAccountWithContext(ctx, account, requestedModel)) && account.IsSchedulableForModelWithContext(ctx, requestedModel) {
						if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
							log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
						}
						return account, nil
					}
				}
			}
		}
	}

	// 2. 获取可调度账号列表（单平台）
	if !accountsLoaded {
		forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string)
		if hasForcePlatform && forcePlatform == "" {
			hasForcePlatform = false
		}
		var err error
		accounts, _, err = s.listSchedulableAccounts(ctx, groupID, platform, hasForcePlatform)
		if err != nil {
			return nil, fmt.Errorf("query accounts failed: %w", err)
		}
	}

	// 3. 按优先级+最久未用选择（考虑模型支持）
	var selected *Account
	for i := range accounts {
		acc := &accounts[i]
		if _, excluded := excludedIDs[acc.ID]; excluded {
			continue
		}
		// Scheduler snapshots can be temporarily stale; re-check schedulability here to
		// avoid selecting accounts that were recently rate-limited/overloaded.
		if !acc.IsSchedulable() {
			continue
		}
		if requestedModel != "" && !s.isModelSupportedByAccountWithContext(ctx, acc, requestedModel) {
			continue
		}
		if !acc.IsSchedulableForModelWithContext(ctx, requestedModel) {
			continue
		}
		if selected == nil {
			selected = acc
			continue
		}
		if acc.Priority < selected.Priority {
			selected = acc
		} else if acc.Priority == selected.Priority {
			switch {
			case acc.LastUsedAt == nil && selected.LastUsedAt != nil:
				selected = acc
			case acc.LastUsedAt != nil && selected.LastUsedAt == nil:
				// keep selected (never used is preferred)
			case acc.LastUsedAt == nil && selected.LastUsedAt == nil:
				if preferOAuth && acc.Type != selected.Type && acc.Type == AccountTypeOAuth {
					selected = acc
				}
			default:
				if acc.LastUsedAt.Before(*selected.LastUsedAt) {
					selected = acc
				}
			}
		}
	}

	if selected == nil {
		if requestedModel != "" {
			return nil, fmt.Errorf("no available accounts supporting model: %s", requestedModel)
		}
		return nil, errors.New("no available accounts")
	}

	// 4. 建立粘性绑定
	if sessionHash != "" && s.cache != nil {
		if err := s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, selected.ID, stickySessionTTL); err != nil {
			log.Printf("set session account failed: session=%s account_id=%d err=%v", sessionHash, selected.ID, err)
		}
	}

	return selected, nil
}

// selectAccountWithMixedScheduling 选择账户（支持混合调度）
// 查询原生平台账户 + 启用 mixed_scheduling 的 antigravity 账户
func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}, nativePlatform string) (*Account, error) {
	preferOAuth := nativePlatform == PlatformGemini
	routingAccountIDs := s.routingAccountIDsForRequest(ctx, groupID, requestedModel, nativePlatform)

	var accounts []Account
	accountsLoaded := false

	// ============ Model Routing (legacy path): apply before sticky session ============
	if len(routingAccountIDs) > 0 {
		if s.debugModelRoutingEnabled() {
			log.Printf("[ModelRoutingDebug] legacy mixed routed begin: group_id=%v model=%s platform=%s session=%s routed_ids=%v",
				derefGroupID(groupID), requestedModel, nativePlatform, shortSessionHash(sessionHash), routingAccountIDs)
		}
		// 1) Sticky session only applies if the bound account is within the routing set.
		if sessionHash != "" && s.cache != nil {
			accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
			if err == nil && accountID > 0 && containsInt64(routingAccountIDs, accountID) {
				if _, excluded := excludedIDs[accountID]; !excluded {
					account, err := s.getSchedulableAccount(ctx, accountID)
					// 检查账号分组归属和有效性：原生平台直接匹配，antigravity 需要启用混合调度
					if err == nil {
						clearSticky := shouldClearStickySession(account, requestedModel)
						if clearSticky {
							_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
						}
						if !clearSticky && s.isAccountInGroup(account, groupID) && (requestedModel == "" || s.isModelSupportedByAccountWithContext(ctx, account, requestedModel)) && account.IsSchedulableForModelWithContext(ctx, requestedModel) {
							if account.Platform == nativePlatform || (account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()) {
								if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
									log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
								}
								if s.debugModelRoutingEnabled() {
									log.Printf("[ModelRoutingDebug] legacy mixed routed sticky hit: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), accountID)
								}
								return account, nil
							}
						}
					}
				}
			}
		}

		// 2) Select an account from the routed candidates.
		var err error
		accounts, _, err = s.listSchedulableAccounts(ctx, groupID, nativePlatform, false)
		if err != nil {
			return nil, fmt.Errorf("query accounts failed: %w", err)
		}
		accountsLoaded = true

		routingSet := make(map[int64]struct{}, len(routingAccountIDs))
		for _, id := range routingAccountIDs {
			if id > 0 {
				routingSet[id] = struct{}{}
			}
		}

		var selected *Account
		for i := range accounts {
			acc := &accounts[i]
			if _, ok := routingSet[acc.ID]; !ok {
				continue
			}
			if _, excluded := excludedIDs[acc.ID]; excluded {
				continue
			}
			// Scheduler snapshots can be temporarily stale; re-check schedulability here to
			// avoid selecting accounts that were recently rate-limited/overloaded.
			if !acc.IsSchedulable() {
				continue
			}
			// 过滤：原生平台直接通过，antigravity 需要启用混合调度
			if acc.Platform == PlatformAntigravity && !acc.IsMixedSchedulingEnabled() {
				continue
			}
			if requestedModel != "" && !s.isModelSupportedByAccountWithContext(ctx, acc, requestedModel) {
				continue
			}
			if !acc.IsSchedulableForModelWithContext(ctx, requestedModel) {
				continue
			}
			if selected == nil {
				selected = acc
				continue
			}
			if acc.Priority < selected.Priority {
				selected = acc
			} else if acc.Priority == selected.Priority {
				switch {
				case acc.LastUsedAt == nil && selected.LastUsedAt != nil:
					selected = acc
				case acc.LastUsedAt != nil && selected.LastUsedAt == nil:
					// keep selected (never used is preferred)
				case acc.LastUsedAt == nil && selected.LastUsedAt == nil:
					if preferOAuth && acc.Platform == PlatformGemini && selected.Platform == PlatformGemini && acc.Type != selected.Type && acc.Type == AccountTypeOAuth {
						selected = acc
					}
				default:
					if acc.LastUsedAt.Before(*selected.LastUsedAt) {
						selected = acc
					}
				}
			}
		}

		if selected != nil {
			if sessionHash != "" && s.cache != nil {
				if err := s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, selected.ID, stickySessionTTL); err != nil {
					log.Printf("set session account failed: session=%s account_id=%d err=%v", sessionHash, selected.ID, err)
				}
			}
			if s.debugModelRoutingEnabled() {
				log.Printf("[ModelRoutingDebug] legacy mixed routed select: group_id=%v model=%s session=%s account=%d", derefGroupID(groupID), requestedModel, shortSessionHash(sessionHash), selected.ID)
			}
			return selected, nil
		}
		log.Printf("[ModelRouting] No routed accounts available for model=%s, falling back to normal selection", requestedModel)
	}

	// 1. 查询粘性会话
	if sessionHash != "" && s.cache != nil {
		accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
		if err == nil && accountID > 0 {
			if _, excluded := excludedIDs[accountID]; !excluded {
				account, err := s.getSchedulableAccount(ctx, accountID)
				// 检查账号分组归属和有效性：原生平台直接匹配，antigravity 需要启用混合调度
				if err == nil {
					clearSticky := shouldClearStickySession(account, requestedModel)
					if clearSticky {
						_ = s.cache.DeleteSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
					}
					if !clearSticky && s.isAccountInGroup(account, groupID) && (requestedModel == "" || s.isModelSupportedByAccountWithContext(ctx, account, requestedModel)) && account.IsSchedulableForModelWithContext(ctx, requestedModel) {
						if account.Platform == nativePlatform || (account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()) {
							if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
								log.Printf("refresh session ttl failed: session=%s err=%v", sessionHash, err)
							}
							return account, nil
						}
					}
				}
			}
		}
	}

	// 2. 获取可调度账号列表
	if !accountsLoaded {
		var err error
		accounts, _, err = s.listSchedulableAccounts(ctx, groupID, nativePlatform, false)
		if err != nil {
			return nil, fmt.Errorf("query accounts failed: %w", err)
		}
	}

	// 3. 按优先级+最久未用选择（考虑模型支持和混合调度）
	var selected *Account
	for i := range accounts {
		acc := &accounts[i]
		if _, excluded := excludedIDs[acc.ID]; excluded {
			continue
		}
		// Scheduler snapshots can be temporarily stale; re-check schedulability here to
		// avoid selecting accounts that were recently rate-limited/overloaded.
		if !acc.IsSchedulable() {
			continue
		}
		// 过滤：原生平台直接通过，antigravity 需要启用混合调度
		if acc.Platform == PlatformAntigravity && !acc.IsMixedSchedulingEnabled() {
			continue
		}
		if requestedModel != "" && !s.isModelSupportedByAccountWithContext(ctx, acc, requestedModel) {
			continue
		}
		if !acc.IsSchedulableForModelWithContext(ctx, requestedModel) {
			continue
		}
		if selected == nil {
			selected = acc
			continue
		}
		if acc.Priority < selected.Priority {
			selected = acc
		} else if acc.Priority == selected.Priority {
			switch {
			case acc.LastUsedAt == nil && selected.LastUsedAt != nil:
				selected = acc
			case acc.LastUsedAt != nil && selected.LastUsedAt == nil:
				// keep selected (never used is preferred)
			case acc.LastUsedAt == nil && selected.LastUsedAt == nil:
				if preferOAuth && acc.Platform == PlatformGemini && selected.Platform == PlatformGemini && acc.Type != selected.Type && acc.Type == AccountTypeOAuth {
					selected = acc
				}
			default:
				if acc.LastUsedAt.Before(*selected.LastUsedAt) {
					selected = acc
				}
			}
		}
	}

	if selected == nil {
		if requestedModel != "" {
			return nil, fmt.Errorf("no available accounts supporting model: %s", requestedModel)
		}
		return nil, errors.New("no available accounts")
	}

	// 4. 建立粘性绑定
	if sessionHash != "" && s.cache != nil {
		if err := s.cache.SetSessionAccountID(ctx, derefGroupID(groupID), sessionHash, selected.ID, stickySessionTTL); err != nil {
			log.Printf("set session account failed: session=%s account_id=%d err=%v", sessionHash, selected.ID, err)
		}
	}

	return selected, nil
}

// isModelSupportedByAccountWithContext 根据账户平台检查模型支持（带 context）
// 对于 Antigravity 平台，会先获取映射后的最终模型名（包括 thinking 后缀）再检查支持
func (s *GatewayService) isModelSupportedByAccountWithContext(ctx context.Context, account *Account, requestedModel string) bool {
	if account.Platform == PlatformAntigravity {
		if strings.TrimSpace(requestedModel) == "" {
			return true
		}
		// 使用与转发阶段一致的映射逻辑：自定义映射优先 → 默认映射兜底
		mapped := mapAntigravityModel(account, requestedModel)
		if mapped == "" {
			return false
		}
		// 应用 thinking 后缀后检查最终模型是否在账号映射中
		if enabled, ok := ctx.Value(ctxkey.ThinkingEnabled).(bool); ok {
			finalModel := applyThinkingModelSuffix(mapped, enabled)
			if finalModel == mapped {
				return true // thinking 后缀未改变模型名，映射已通过
			}
			return account.IsModelSupported(finalModel)
		}
		return true
	}
	return s.isModelSupportedByAccount(account, requestedModel)
}

// isModelSupportedByAccount 根据账户平台检查模型支持（无 context，用于非 Antigravity 平台）
func (s *GatewayService) isModelSupportedByAccount(account *Account, requestedModel string) bool {
	if account.Platform == PlatformAntigravity {
		if strings.TrimSpace(requestedModel) == "" {
			return true
		}
		return mapAntigravityModel(account, requestedModel) != ""
	}
	// OAuth/SetupToken 账号使用 Anthropic 标准映射（短ID → 长ID）
	if account.Platform == PlatformAnthropic && account.Type != AccountTypeAPIKey {
		requestedModel = claude.NormalizeModelID(requestedModel)
	}
	// Gemini API Key 账户直接透传，由上游判断模型是否支持
	if account.Platform == PlatformGemini && account.Type == AccountTypeAPIKey {
		return true
	}
	// 其他平台使用账户的模型支持检查
	return account.IsModelSupported(requestedModel)
}

// GetAccessToken 获取账号凭证
func (s *GatewayService) GetAccessToken(ctx context.Context, account *Account) (string, string, error) {
	switch account.Type {
	case AccountTypeOAuth, AccountTypeSetupToken:
		// Both oauth and setup-token use OAuth token flow
		return s.getOAuthToken(ctx, account)
	case AccountTypeAPIKey:
		apiKey := account.GetCredential("api_key")
		if apiKey == "" {
			return "", "", errors.New("api_key not found in credentials")
		}
		return apiKey, "apikey", nil
	default:
		return "", "", fmt.Errorf("unsupported account type: %s", account.Type)
	}
}

func (s *GatewayService) getOAuthToken(ctx context.Context, account *Account) (string, string, error) {
	// 对于 Anthropic OAuth 账号，使用 ClaudeTokenProvider 获取缓存的 token
	if account.Platform == PlatformAnthropic && account.Type == AccountTypeOAuth && s.claudeTokenProvider != nil {
		accessToken, err := s.claudeTokenProvider.GetAccessToken(ctx, account)
		if err != nil {
			return "", "", err
		}
		return accessToken, "oauth", nil
	}

	// 其他情况（Gemini 有自己的 TokenProvider，setup-token 类型等）直接从账号读取
	accessToken := account.GetCredential("access_token")
	if accessToken == "" {
		return "", "", errors.New("access_token not found in credentials")
	}
	// Token刷新由后台 TokenRefreshService 处理，此处只返回当前token
	return accessToken, "oauth", nil
}

// 重试相关常量
const (
	// 最大尝试次数（包含首次请求）。过多重试会导致请求堆积与资源耗尽。
	maxRetryAttempts = 5

	// 指数退避：第 N 次失败后的等待 = retryBaseDelay * 2^(N-1)，并且上限为 retryMaxDelay。
	retryBaseDelay = 300 * time.Millisecond
	retryMaxDelay  = 3 * time.Second

	// 最大重试耗时（包含请求本身耗时 + 退避等待时间）。
	// 用于防止极端情况下 goroutine 长时间堆积导致资源耗尽。
	maxRetryElapsed = 10 * time.Second
)

func (s *GatewayService) shouldRetryUpstreamError(account *Account, statusCode int) bool {
	// OAuth/Setup Token 账号：仅 403 重试
	if account.IsOAuth() {
		return statusCode == 403
	}

	// API Key 账号：未配置的错误码重试
	return !account.ShouldHandleErrorCode(statusCode)
}

// shouldFailoverUpstreamError determines whether an upstream error should trigger account failover.
func (s *GatewayService) shouldFailoverUpstreamError(statusCode int) bool {
	switch statusCode {
	case 401, 403, 429, 529:
		return true
	default:
		return statusCode >= 500
	}
}

func retryBackoffDelay(attempt int) time.Duration {
	// attempt 从 1 开始，表示第 attempt 次请求刚失败，需要等待后进行第 attempt+1 次请求。
	if attempt <= 0 {
		return retryBaseDelay
	}
	delay := retryBaseDelay * time.Duration(1<<(attempt-1))
	if delay > retryMaxDelay {
		return retryMaxDelay
	}
	return delay
}

func sleepWithContext(ctx context.Context, d time.Duration) error {
	if d <= 0 {
		return nil
	}
	timer := time.NewTimer(d)
	defer func() {
		if !timer.Stop() {
			select {
			case <-timer.C:
			default:
			}
		}
	}()

	select {
	case <-ctx.Done():
		return ctx.Err()
	case <-timer.C:
		return nil
	}
}

// isClaudeCodeClient 判断请求是否来自 Claude Code 客户端
// 简化判断：User-Agent 匹配 + metadata.user_id 存在
func isClaudeCodeClient(userAgent string, metadataUserID string) bool {
	if metadataUserID == "" {
		return false
	}
	return claudeCliUserAgentRe.MatchString(userAgent)
}

func isClaudeCodeRequest(ctx context.Context, c *gin.Context, parsed *ParsedRequest) bool {
	if IsClaudeCodeClient(ctx) {
		return true
	}
	if parsed == nil || c == nil {
		return false
	}
	return isClaudeCodeClient(c.GetHeader("User-Agent"), parsed.MetadataUserID)
}

// systemIncludesClaudeCodePrompt 检查 system 中是否已包含 Claude Code 提示词
// 使用前缀匹配支持多种变体（标准版、Agent SDK 版等）
func systemIncludesClaudeCodePrompt(system any) bool {
	switch v := system.(type) {
	case string:
		return hasClaudeCodePrefix(v)
	case []any:
		for _, item := range v {
			if m, ok := item.(map[string]any); ok {
				if text, ok := m["text"].(string); ok && hasClaudeCodePrefix(text) {
					return true
				}
			}
		}
	}
	return false
}

// hasClaudeCodePrefix 检查文本是否以 Claude Code 提示词的特征前缀开头
func hasClaudeCodePrefix(text string) bool {
	for _, prefix := range claudeCodePromptPrefixes {
		if strings.HasPrefix(text, prefix) {
			return true
		}
	}
	return false
}

// injectClaudeCodePrompt 在 system 开头注入 Claude Code 提示词
// 处理 null、字符串、数组三种格式
func injectClaudeCodePrompt(body []byte, system any) []byte {
	claudeCodeBlock := map[string]any{
		"type":          "text",
		"text":          claudeCodeSystemPrompt,
		"cache_control": map[string]string{"type": "ephemeral"},
	}
	// Opencode plugin applies an extra safeguard: it not only prepends the Claude Code
	// banner, it also prefixes the next system instruction with the same banner plus
	// a blank line. This helps when upstream concatenates system instructions.
	claudeCodePrefix := strings.TrimSpace(claudeCodeSystemPrompt)

	var newSystem []any

	switch v := system.(type) {
	case nil:
		newSystem = []any{claudeCodeBlock}
	case string:
		// Be tolerant of older/newer clients that may differ only by trailing whitespace/newlines.
		if strings.TrimSpace(v) == "" || strings.TrimSpace(v) == strings.TrimSpace(claudeCodeSystemPrompt) {
			newSystem = []any{claudeCodeBlock}
		} else {
			// Mirror opencode behavior: keep the banner as a separate system entry,
			// but also prefix the next system text with the banner.
			merged := v
			if !strings.HasPrefix(v, claudeCodePrefix) {
				merged = claudeCodePrefix + "\n\n" + v
			}
			newSystem = []any{claudeCodeBlock, map[string]any{"type": "text", "text": merged}}
		}
	case []any:
		newSystem = make([]any, 0, len(v)+1)
		newSystem = append(newSystem, claudeCodeBlock)
		prefixedNext := false
		for _, item := range v {
			if m, ok := item.(map[string]any); ok {
				if text, ok := m["text"].(string); ok && strings.TrimSpace(text) == strings.TrimSpace(claudeCodeSystemPrompt) {
					continue
				}
				// Prefix the first subsequent text system block once.
				if !prefixedNext {
					if blockType, _ := m["type"].(string); blockType == "text" {
						if text, ok := m["text"].(string); ok && strings.TrimSpace(text) != "" && !strings.HasPrefix(text, claudeCodePrefix) {
							m["text"] = claudeCodePrefix + "\n\n" + text
							prefixedNext = true
						}
					}
				}
			}
			newSystem = append(newSystem, item)
		}
	default:
		newSystem = []any{claudeCodeBlock}
	}

	result, err := sjson.SetBytes(body, "system", newSystem)
	if err != nil {
		log.Printf("Warning: failed to inject Claude Code prompt: %v", err)
		return body
	}
	return result
}

// enforceCacheControlLimit 强制执行 cache_control 块数量限制（最多 4 个）
// 超限时优先从 messages 中移除 cache_control，保护 system 中的缓存控制
func enforceCacheControlLimit(body []byte) []byte {
	var data map[string]any
	if err := json.Unmarshal(body, &data); err != nil {
		return body
	}

	// 清理 thinking 块中的非法 cache_control（thinking 块不支持该字段）
	removeCacheControlFromThinkingBlocks(data)

	// 计算当前 cache_control 块数量
	count := countCacheControlBlocks(data)
	if count <= maxCacheControlBlocks {
		return body
	}

	// 超限：优先从 messages 中移除，再从 system 中移除
	for count > maxCacheControlBlocks {
		if removeCacheControlFromMessages(data) {
			count--
			continue
		}
		if removeCacheControlFromSystem(data) {
			count--
			continue
		}
		break
	}

	result, err := json.Marshal(data)
	if err != nil {
		return body
	}
	return result
}

// countCacheControlBlocks 统计 system 和 messages 中的 cache_control 块数量
// 注意：thinking 块不支持 cache_control，统计时跳过
func countCacheControlBlocks(data map[string]any) int {
	count := 0

	// 统计 system 中的块
	if system, ok := data["system"].([]any); ok {
		for _, item := range system {
			if m, ok := item.(map[string]any); ok {
				// thinking 块不支持 cache_control，跳过
				if blockType, _ := m["type"].(string); blockType == "thinking" {
					continue
				}
				if _, has := m["cache_control"]; has {
					count++
				}
			}
		}
	}

	// 统计 messages 中的块
	if messages, ok := data["messages"].([]any); ok {
		for _, msg := range messages {
			if msgMap, ok := msg.(map[string]any); ok {
				if content, ok := msgMap["content"].([]any); ok {
					for _, item := range content {
						if m, ok := item.(map[string]any); ok {
							// thinking 块不支持 cache_control，跳过
							if blockType, _ := m["type"].(string); blockType == "thinking" {
								continue
							}
							if _, has := m["cache_control"]; has {
								count++
							}
						}
					}
				}
			}
		}
	}

	return count
}

// removeCacheControlFromMessages 从 messages 中移除一个 cache_control（从头开始）
// 返回 true 表示成功移除，false 表示没有可移除的
// 注意：跳过 thinking 块（它不支持 cache_control）
func removeCacheControlFromMessages(data map[string]any) bool {
	messages, ok := data["messages"].([]any)
	if !ok {
		return false
	}

	for _, msg := range messages {
		msgMap, ok := msg.(map[string]any)
		if !ok {
			continue
		}
		content, ok := msgMap["content"].([]any)
		if !ok {
			continue
		}
		for _, item := range content {
			if m, ok := item.(map[string]any); ok {
				// thinking 块不支持 cache_control，跳过
				if blockType, _ := m["type"].(string); blockType == "thinking" {
					continue
				}
				if _, has := m["cache_control"]; has {
					delete(m, "cache_control")
					return true
				}
			}
		}
	}
	return false
}

// removeCacheControlFromSystem 从 system 中移除一个 cache_control（从尾部开始，保护注入的 prompt）
// 返回 true 表示成功移除，false 表示没有可移除的
// 注意：跳过 thinking 块（它不支持 cache_control）
func removeCacheControlFromSystem(data map[string]any) bool {
	system, ok := data["system"].([]any)
	if !ok {
		return false
	}

	// 从尾部开始移除，保护开头注入的 Claude Code prompt
	for i := len(system) - 1; i >= 0; i-- {
		if m, ok := system[i].(map[string]any); ok {
			// thinking 块不支持 cache_control，跳过
			if blockType, _ := m["type"].(string); blockType == "thinking" {
				continue
			}
			if _, has := m["cache_control"]; has {
				delete(m, "cache_control")
				return true
			}
		}
	}
	return false
}

// removeCacheControlFromThinkingBlocks 强制清理所有 thinking 块中的非法 cache_control
// thinking 块不支持 cache_control 字段，这个函数确保所有 thinking 块都不含该字段
func removeCacheControlFromThinkingBlocks(data map[string]any) {
	// 清理 system 中的 thinking 块
	if system, ok := data["system"].([]any); ok {
		for _, item := range system {
			if m, ok := item.(map[string]any); ok {
				if blockType, _ := m["type"].(string); blockType == "thinking" {
					if _, has := m["cache_control"]; has {
						delete(m, "cache_control")
						log.Printf("[Warning] Removed illegal cache_control from thinking block in system")
					}
				}
			}
		}
	}

	// 清理 messages 中的 thinking 块
	if messages, ok := data["messages"].([]any); ok {
		for msgIdx, msg := range messages {
			if msgMap, ok := msg.(map[string]any); ok {
				if content, ok := msgMap["content"].([]any); ok {
					for contentIdx, item := range content {
						if m, ok := item.(map[string]any); ok {
							if blockType, _ := m["type"].(string); blockType == "thinking" {
								if _, has := m["cache_control"]; has {
									delete(m, "cache_control")
									log.Printf("[Warning] Removed illegal cache_control from thinking block in messages[%d].content[%d]", msgIdx, contentIdx)
								}
							}
						}
					}
				}
			}
		}
	}
}

// Forward 转发请求到Claude API
func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *Account, parsed *ParsedRequest) (*ForwardResult, error) {
	startTime := time.Now()
	if parsed == nil {
		return nil, fmt.Errorf("parse request: empty request")
	}

	body := parsed.Body
	reqModel := parsed.Model
	reqStream := parsed.Stream
	originalModel := reqModel

	isClaudeCode := isClaudeCodeRequest(ctx, c, parsed)
	shouldMimicClaudeCode := account.IsOAuth() && !isClaudeCode

	if shouldMimicClaudeCode {
		// 智能注入 Claude Code 系统提示词（仅 OAuth/SetupToken 账号需要）
		// 条件：1) OAuth/SetupToken 账号  2) 不是 Claude Code 客户端  3) 不是 Haiku 模型  4) system 中还没有 Claude Code 提示词
		if !strings.Contains(strings.ToLower(reqModel), "haiku") &&
			!systemIncludesClaudeCodePrompt(parsed.System) {
			body = injectClaudeCodePrompt(body, parsed.System)
		}

		normalizeOpts := claudeOAuthNormalizeOptions{stripSystemCacheControl: true}
		if s.identityService != nil {
			fp, err := s.identityService.GetOrCreateFingerprint(ctx, account.ID, c.Request.Header)
			if err == nil && fp != nil {
				if metadataUserID := s.buildOAuthMetadataUserID(parsed, account, fp); metadataUserID != "" {
					normalizeOpts.injectMetadata = true
					normalizeOpts.metadataUserID = metadataUserID
				}
			}
		}

		body, reqModel = normalizeClaudeOAuthRequestBody(body, reqModel, normalizeOpts)
	}

	// 强制执行 cache_control 块数量限制（最多 4 个）
	body = enforceCacheControlLimit(body)

	// 应用模型映射：
	// - APIKey 账号：使用账号级别的显式映射（如果配置），否则透传原始模型名
	// - OAuth/SetupToken 账号：使用 Anthropic 标准映射（短ID → 长ID）
	mappedModel := reqModel
	mappingSource := ""
	if account.Type == AccountTypeAPIKey {
		mappedModel = account.GetMappedModel(reqModel)
		if mappedModel != reqModel {
			mappingSource = "account"
		}
	}
	if mappingSource == "" && account.Platform == PlatformAnthropic && account.Type != AccountTypeAPIKey {
		normalized := claude.NormalizeModelID(reqModel)
		if normalized != reqModel {
			mappedModel = normalized
			mappingSource = "prefix"
		}
	}
	if mappedModel != reqModel {
		// 替换请求体中的模型名
		body = s.replaceModelInBody(body, mappedModel)
		reqModel = mappedModel
		log.Printf("Model mapping applied: %s -> %s (account: %s, source=%s)", originalModel, mappedModel, account.Name, mappingSource)
	}

	// 获取凭证
	token, tokenType, err := s.GetAccessToken(ctx, account)
	if err != nil {
		return nil, err
	}

	// 获取代理URL
	proxyURL := ""
	if account.ProxyID != nil && account.Proxy != nil {
		proxyURL = account.Proxy.URL()
	}

	// 调试日志：记录即将转发的账号信息
	log.Printf("[Forward] Using account: ID=%d Name=%s Platform=%s Type=%s TLSFingerprint=%v Proxy=%s",
		account.ID, account.Name, account.Platform, account.Type, account.IsTLSFingerprintEnabled(), proxyURL)

	// 重试循环
	var resp *http.Response
	retryStart := time.Now()
	for attempt := 1; attempt <= maxRetryAttempts; attempt++ {
		// 构建上游请求（每次重试需要重新构建，因为请求体需要重新读取）
		// Capture upstream request body for ops retry of this attempt.
		c.Set(OpsUpstreamRequestBodyKey, string(body))
		upstreamReq, err := s.buildUpstreamRequest(ctx, c, account, body, token, tokenType, reqModel, reqStream, shouldMimicClaudeCode)
		if err != nil {
			return nil, err
		}

		// 发送请求
		resp, err = s.httpUpstream.DoWithTLS(upstreamReq, proxyURL, account.ID, account.Concurrency, account.IsTLSFingerprintEnabled())
		if err != nil {
			if resp != nil && resp.Body != nil {
				_ = resp.Body.Close()
			}
			// Ensure the client receives an error response (handlers assume Forward writes on non-failover errors).
			safeErr := sanitizeUpstreamErrorMessage(err.Error())
			setOpsUpstreamError(c, 0, safeErr, "")
			appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
				Platform:           account.Platform,
				AccountID:          account.ID,
				AccountName:        account.Name,
				UpstreamStatusCode: 0,
				Kind:               "request_error",
				Message:            safeErr,
			})
			c.JSON(http.StatusBadGateway, gin.H{
				"type": "error",
				"error": gin.H{
					"type":    "upstream_error",
					"message": "Upstream request failed",
				},
			})
			return nil, fmt.Errorf("upstream request failed: %s", safeErr)
		}

		// 优先检测thinking block签名错误（400）并重试一次
		if resp.StatusCode == 400 {
			respBody, readErr := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
			if readErr == nil {
				_ = resp.Body.Close()

				if s.isThinkingBlockSignatureError(respBody) {
					appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
						Platform:           account.Platform,
						AccountID:          account.ID,
						AccountName:        account.Name,
						UpstreamStatusCode: resp.StatusCode,
						UpstreamRequestID:  resp.Header.Get("x-request-id"),
						Kind:               "signature_error",
						Message:            extractUpstreamErrorMessage(respBody),
						Detail: func() string {
							if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
								return truncateString(string(respBody), s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes)
							}
							return ""
						}(),
					})

					looksLikeToolSignatureError := func(msg string) bool {
						m := strings.ToLower(msg)
						return strings.Contains(m, "tool_use") ||
							strings.Contains(m, "tool_result") ||
							strings.Contains(m, "functioncall") ||
							strings.Contains(m, "function_call") ||
							strings.Contains(m, "functionresponse") ||
							strings.Contains(m, "function_response")
					}

					// 避免在重试预算已耗尽时再发起额外请求
					if time.Since(retryStart) >= maxRetryElapsed {
						resp.Body = io.NopCloser(bytes.NewReader(respBody))
						break
					}
					log.Printf("Account %d: detected thinking block signature error, retrying with filtered thinking blocks", account.ID)

					// Conservative two-stage fallback:
					// 1) Disable thinking + thinking->text (preserve content)
					// 2) Only if upstream still errors AND error message points to tool/function signature issues:
					//    also downgrade tool_use/tool_result blocks to text.

					filteredBody := FilterThinkingBlocksForRetry(body)
					retryReq, buildErr := s.buildUpstreamRequest(ctx, c, account, filteredBody, token, tokenType, reqModel, reqStream, shouldMimicClaudeCode)
					if buildErr == nil {
						retryResp, retryErr := s.httpUpstream.DoWithTLS(retryReq, proxyURL, account.ID, account.Concurrency, account.IsTLSFingerprintEnabled())
						if retryErr == nil {
							if retryResp.StatusCode < 400 {
								log.Printf("Account %d: signature error retry succeeded (thinking downgraded)", account.ID)
								resp = retryResp
								break
							}

							retryRespBody, retryReadErr := io.ReadAll(io.LimitReader(retryResp.Body, 2<<20))
							_ = retryResp.Body.Close()
							if retryReadErr == nil && retryResp.StatusCode == 400 && s.isThinkingBlockSignatureError(retryRespBody) {
								appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
									Platform:           account.Platform,
									AccountID:          account.ID,
									AccountName:        account.Name,
									UpstreamStatusCode: retryResp.StatusCode,
									UpstreamRequestID:  retryResp.Header.Get("x-request-id"),
									Kind:               "signature_retry_thinking",
									Message:            extractUpstreamErrorMessage(retryRespBody),
									Detail: func() string {
										if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
											return truncateString(string(retryRespBody), s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes)
										}
										return ""
									}(),
								})
								msg2 := extractUpstreamErrorMessage(retryRespBody)
								if looksLikeToolSignatureError(msg2) && time.Since(retryStart) < maxRetryElapsed {
									log.Printf("Account %d: signature retry still failing and looks tool-related, retrying with tool blocks downgraded", account.ID)
									filteredBody2 := FilterSignatureSensitiveBlocksForRetry(body)
									retryReq2, buildErr2 := s.buildUpstreamRequest(ctx, c, account, filteredBody2, token, tokenType, reqModel, reqStream, shouldMimicClaudeCode)
									if buildErr2 == nil {
										retryResp2, retryErr2 := s.httpUpstream.DoWithTLS(retryReq2, proxyURL, account.ID, account.Concurrency, account.IsTLSFingerprintEnabled())
										if retryErr2 == nil {
											resp = retryResp2
											break
										}
										if retryResp2 != nil && retryResp2.Body != nil {
											_ = retryResp2.Body.Close()
										}
										appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
											Platform:           account.Platform,
											AccountID:          account.ID,
											AccountName:        account.Name,
											UpstreamStatusCode: 0,
											Kind:               "signature_retry_tools_request_error",
											Message:            sanitizeUpstreamErrorMessage(retryErr2.Error()),
										})
										log.Printf("Account %d: tool-downgrade signature retry failed: %v", account.ID, retryErr2)
									} else {
										log.Printf("Account %d: tool-downgrade signature retry build failed: %v", account.ID, buildErr2)
									}
								}
							}

							// Fall back to the original retry response context.
							resp = &http.Response{
								StatusCode: retryResp.StatusCode,
								Header:     retryResp.Header.Clone(),
								Body:       io.NopCloser(bytes.NewReader(retryRespBody)),
							}
							break
						}
						if retryResp != nil && retryResp.Body != nil {
							_ = retryResp.Body.Close()
						}
						log.Printf("Account %d: signature error retry failed: %v", account.ID, retryErr)
					} else {
						log.Printf("Account %d: signature error retry build request failed: %v", account.ID, buildErr)
					}

					// Retry failed: restore original response body and continue handling.
					resp.Body = io.NopCloser(bytes.NewReader(respBody))
					break
				}
				// 不是thinking签名错误，恢复响应体
				resp.Body = io.NopCloser(bytes.NewReader(respBody))
			}
		}

		// 检查是否需要通用重试（排除400，因为400已经在上面特殊处理过了）
		if resp.StatusCode >= 400 && resp.StatusCode != 400 && s.shouldRetryUpstreamError(account, resp.StatusCode) {
			if attempt < maxRetryAttempts {
				elapsed := time.Since(retryStart)
				if elapsed >= maxRetryElapsed {
					break
				}

				delay := retryBackoffDelay(attempt)
				remaining := maxRetryElapsed - elapsed
				if delay > remaining {
					delay = remaining
				}
				if delay <= 0 {
					break
				}

				respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
				_ = resp.Body.Close()
				appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
					Platform:           account.Platform,
					AccountID:          account.ID,
					AccountName:        account.Name,
					UpstreamStatusCode: resp.StatusCode,
					UpstreamRequestID:  resp.Header.Get("x-request-id"),
					Kind:               "retry",
					Message:            extractUpstreamErrorMessage(respBody),
					Detail: func() string {
						if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
							return truncateString(string(respBody), s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes)
						}
						return ""
					}(),
				})
				log.Printf("Account %d: upstream error %d, retry %d/%d after %v (elapsed=%v/%v)",
					account.ID, resp.StatusCode, attempt, maxRetryAttempts, delay, elapsed, maxRetryElapsed)
				if err := sleepWithContext(ctx, delay); err != nil {
					return nil, err
				}
				continue
			}
			// 最后一次尝试也失败，跳出循环处理重试耗尽
			break
		}

		// 不需要重试（成功或不可重试的错误），跳出循环
		// DEBUG: 输出响应 headers（用于检测 rate limit 信息）
		if account.Platform == PlatformGemini && resp.StatusCode < 400 {
			log.Printf("[DEBUG] Gemini API Response Headers for account %d:", account.ID)
			for k, v := range resp.Header {
				log.Printf("[DEBUG]   %s: %v", k, v)
			}
		}
		break
	}
	if resp == nil || resp.Body == nil {
		return nil, errors.New("upstream request failed: empty response")
	}
	defer func() { _ = resp.Body.Close() }()

	// 处理重试耗尽的情况
	if resp.StatusCode >= 400 && s.shouldRetryUpstreamError(account, resp.StatusCode) {
		if s.shouldFailoverUpstreamError(resp.StatusCode) {
			respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
			_ = resp.Body.Close()
			resp.Body = io.NopCloser(bytes.NewReader(respBody))

			// 调试日志：打印重试耗尽后的错误响应
			log.Printf("[Forward] Upstream error (retry exhausted, failover): Account=%d(%s) Status=%d RequestID=%s Body=%s",
				account.ID, account.Name, resp.StatusCode, resp.Header.Get("x-request-id"), truncateString(string(respBody), 1000))

			s.handleRetryExhaustedSideEffects(ctx, resp, account)
			appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
				Platform:           account.Platform,
				AccountID:          account.ID,
				AccountName:        account.Name,
				UpstreamStatusCode: resp.StatusCode,
				UpstreamRequestID:  resp.Header.Get("x-request-id"),
				Kind:               "retry_exhausted_failover",
				Message:            extractUpstreamErrorMessage(respBody),
				Detail: func() string {
					if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
						return truncateString(string(respBody), s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes)
					}
					return ""
				}(),
			})
			return nil, &UpstreamFailoverError{StatusCode: resp.StatusCode, ResponseBody: respBody}
		}
		return s.handleRetryExhaustedError(ctx, resp, c, account)
	}

	// 处理可切换账号的错误
	if resp.StatusCode >= 400 && s.shouldFailoverUpstreamError(resp.StatusCode) {
		respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
		_ = resp.Body.Close()
		resp.Body = io.NopCloser(bytes.NewReader(respBody))

		// 调试日志：打印上游错误响应
		log.Printf("[Forward] Upstream error (failover): Account=%d(%s) Status=%d RequestID=%s Body=%s",
			account.ID, account.Name, resp.StatusCode, resp.Header.Get("x-request-id"), truncateString(string(respBody), 1000))

		s.handleFailoverSideEffects(ctx, resp, account)
		appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
			Platform:           account.Platform,
			AccountID:          account.ID,
			UpstreamStatusCode: resp.StatusCode,
			UpstreamRequestID:  resp.Header.Get("x-request-id"),
			Kind:               "failover",
			Message:            extractUpstreamErrorMessage(respBody),
			Detail: func() string {
				if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
					return truncateString(string(respBody), s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes)
				}
				return ""
			}(),
		})
		return nil, &UpstreamFailoverError{StatusCode: resp.StatusCode, ResponseBody: respBody}
	}
	if resp.StatusCode >= 400 {
		// 可选：对部分 400 触发 failover（默认关闭以保持语义）
		if resp.StatusCode == 400 && s.cfg != nil && s.cfg.Gateway.FailoverOn400 {
			respBody, readErr := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
			if readErr != nil {
				// ReadAll failed, fall back to normal error handling without consuming the stream
				return s.handleErrorResponse(ctx, resp, c, account)
			}
			_ = resp.Body.Close()
			resp.Body = io.NopCloser(bytes.NewReader(respBody))

			if s.shouldFailoverOn400(respBody) {
				upstreamMsg := strings.TrimSpace(extractUpstreamErrorMessage(respBody))
				upstreamMsg = sanitizeUpstreamErrorMessage(upstreamMsg)
				upstreamDetail := ""
				if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
					maxBytes := s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes
					if maxBytes <= 0 {
						maxBytes = 2048
					}
					upstreamDetail = truncateString(string(respBody), maxBytes)
				}
				appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
					Platform:           account.Platform,
					AccountID:          account.ID,
					AccountName:        account.Name,
					UpstreamStatusCode: resp.StatusCode,
					UpstreamRequestID:  resp.Header.Get("x-request-id"),
					Kind:               "failover_on_400",
					Message:            upstreamMsg,
					Detail:             upstreamDetail,
				})

				if s.cfg.Gateway.LogUpstreamErrorBody {
					log.Printf(
						"Account %d: 400 error, attempting failover: %s",
						account.ID,
						truncateForLog(respBody, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes),
					)
				} else {
					log.Printf("Account %d: 400 error, attempting failover", account.ID)
				}
				s.handleFailoverSideEffects(ctx, resp, account)
				return nil, &UpstreamFailoverError{StatusCode: resp.StatusCode, ResponseBody: respBody}
			}
		}
		return s.handleErrorResponse(ctx, resp, c, account)
	}

	// 处理正常响应
	var usage *ClaudeUsage
	var firstTokenMs *int
	var clientDisconnect bool
	if reqStream {
		streamResult, err := s.handleStreamingResponse(ctx, resp, c, account, startTime, originalModel, reqModel, shouldMimicClaudeCode)
		if err != nil {
			if err.Error() == "have error in stream" {
				return nil, &UpstreamFailoverError{
					StatusCode: 403,
				}
			}
			return nil, err
		}
		usage = streamResult.usage
		firstTokenMs = streamResult.firstTokenMs
		clientDisconnect = streamResult.clientDisconnect
	} else {
		usage, err = s.handleNonStreamingResponse(ctx, resp, c, account, originalModel, reqModel)
		if err != nil {
			return nil, err
		}
	}

	return &ForwardResult{
		RequestID:        resp.Header.Get("x-request-id"),
		Usage:            *usage,
		Model:            originalModel, // 使用原始模型用于计费和日志
		Stream:           reqStream,
		Duration:         time.Since(startTime),
		FirstTokenMs:     firstTokenMs,
		ClientDisconnect: clientDisconnect,
	}, nil
}

func (s *GatewayService) buildUpstreamRequest(ctx context.Context, c *gin.Context, account *Account, body []byte, token, tokenType, modelID string, reqStream bool, mimicClaudeCode bool) (*http.Request, error) {
	// 确定目标URL
	targetURL := claudeAPIURL
	if account.Type == AccountTypeAPIKey {
		baseURL := account.GetBaseURL()
		if baseURL != "" {
			validatedURL, err := s.validateUpstreamBaseURL(baseURL)
			if err != nil {
				return nil, err
			}
			targetURL = validatedURL + "/v1/messages"
		}
	}

	clientHeaders := http.Header{}
	if c != nil && c.Request != nil {
		clientHeaders = c.Request.Header
	}

	// OAuth账号：应用统一指纹
	var fingerprint *Fingerprint
	if account.IsOAuth() && s.identityService != nil {
		// 1. 获取或创建指纹（包含随机生成的ClientID）
		fp, err := s.identityService.GetOrCreateFingerprint(ctx, account.ID, clientHeaders)
		if err != nil {
			log.Printf("Warning: failed to get fingerprint for account %d: %v", account.ID, err)
			// 失败时降级为透传原始headers
		} else {
			fingerprint = fp

			// 2. 重写metadata.user_id（需要指纹中的ClientID和账号的account_uuid）
			// 如果启用了会话ID伪装，会在重写后替换 session 部分为固定值
			accountUUID := account.GetExtraString("account_uuid")
			if accountUUID != "" && fp.ClientID != "" {
				if newBody, err := s.identityService.RewriteUserIDWithMasking(ctx, body, account, accountUUID, fp.ClientID); err == nil && len(newBody) > 0 {
					body = newBody
				}
			}
		}
	}

	req, err := http.NewRequestWithContext(ctx, "POST", targetURL, bytes.NewReader(body))
	if err != nil {
		return nil, err
	}

	// 设置认证头
	if tokenType == "oauth" {
		req.Header.Set("authorization", "Bearer "+token)
	} else {
		req.Header.Set("x-api-key", token)
	}

	// 白名单透传headers
	for key, values := range clientHeaders {
		lowerKey := strings.ToLower(key)
		if allowedHeaders[lowerKey] {
			for _, v := range values {
				req.Header.Add(key, v)
			}
		}
	}

	// OAuth账号：应用缓存的指纹到请求头（覆盖白名单透传的头）
	if fingerprint != nil {
		s.identityService.ApplyFingerprint(req, fingerprint)
	}

	// 确保必要的headers存在
	if req.Header.Get("content-type") == "" {
		req.Header.Set("content-type", "application/json")
	}
	if req.Header.Get("anthropic-version") == "" {
		req.Header.Set("anthropic-version", "2023-06-01")
	}
	if tokenType == "oauth" {
		applyClaudeOAuthHeaderDefaults(req, reqStream)
	}

	// 处理 anthropic-beta header（OAuth 账号需要包含 oauth beta）
	if tokenType == "oauth" {
		if mimicClaudeCode {
			// 非 Claude Code 客户端：按 opencode 的策略处理：
			// - 强制 Claude Code 指纹相关请求头（尤其是 user-agent/x-stainless/x-app）
			// - 保留 incoming beta 的同时，确保 OAuth 所需 beta 存在
			applyClaudeCodeMimicHeaders(req, reqStream)

			incomingBeta := req.Header.Get("anthropic-beta")
			// Match real Claude CLI traffic (per mitmproxy reports):
			// messages requests typically use only oauth + interleaved-thinking.
			// Also drop claude-code beta if a downstream client added it.
			requiredBetas := []string{claude.BetaOAuth, claude.BetaInterleavedThinking}
			drop := map[string]struct{}{claude.BetaClaudeCode: {}}
			req.Header.Set("anthropic-beta", mergeAnthropicBetaDropping(requiredBetas, incomingBeta, drop))
		} else {
			// Claude Code 客户端：尽量透传原始 header，仅补齐 oauth beta
			clientBetaHeader := req.Header.Get("anthropic-beta")
			req.Header.Set("anthropic-beta", s.getBetaHeader(modelID, clientBetaHeader))
		}
	} else if s.cfg != nil && s.cfg.Gateway.InjectBetaForAPIKey && req.Header.Get("anthropic-beta") == "" {
		// API-key：仅在请求显式使用 beta 特性且客户端未提供时，按需补齐（默认关闭）
		if requestNeedsBetaFeatures(body) {
			if beta := defaultAPIKeyBetaHeader(body); beta != "" {
				req.Header.Set("anthropic-beta", beta)
			}
		}
	}

	// Always capture a compact fingerprint line for later error diagnostics.
	// We only print it when needed (or when the explicit debug flag is enabled).
	if c != nil && tokenType == "oauth" {
		c.Set(claudeMimicDebugInfoKey, buildClaudeMimicDebugLine(req, body, account, tokenType, mimicClaudeCode))
	}
	if s.debugClaudeMimicEnabled() {
		logClaudeMimicDebug(req, body, account, tokenType, mimicClaudeCode)
	}

	return req, nil
}

// getBetaHeader 处理anthropic-beta header
// 对于OAuth账号，需要确保包含oauth-2025-04-20
func (s *GatewayService) getBetaHeader(modelID string, clientBetaHeader string) string {
	// 如果客户端传了anthropic-beta
	if clientBetaHeader != "" {
		// 已包含oauth beta则直接返回
		if strings.Contains(clientBetaHeader, claude.BetaOAuth) {
			return clientBetaHeader
		}

		// 需要添加oauth beta
		parts := strings.Split(clientBetaHeader, ",")
		for i, p := range parts {
			parts[i] = strings.TrimSpace(p)
		}

		// 在claude-code-20250219后面插入oauth beta
		claudeCodeIdx := -1
		for i, p := range parts {
			if p == claude.BetaClaudeCode {
				claudeCodeIdx = i
				break
			}
		}

		if claudeCodeIdx >= 0 {
			// 在claude-code后面插入
			newParts := make([]string, 0, len(parts)+1)
			newParts = append(newParts, parts[:claudeCodeIdx+1]...)
			newParts = append(newParts, claude.BetaOAuth)
			newParts = append(newParts, parts[claudeCodeIdx+1:]...)
			return strings.Join(newParts, ",")
		}

		// 没有claude-code，放在第一位
		return claude.BetaOAuth + "," + clientBetaHeader
	}

	// 客户端没传，根据模型生成
	// haiku 模型不需要 claude-code beta
	if strings.Contains(strings.ToLower(modelID), "haiku") {
		return claude.HaikuBetaHeader
	}

	return claude.DefaultBetaHeader
}

func requestNeedsBetaFeatures(body []byte) bool {
	tools := gjson.GetBytes(body, "tools")
	if tools.Exists() && tools.IsArray() && len(tools.Array()) > 0 {
		return true
	}
	if strings.EqualFold(gjson.GetBytes(body, "thinking.type").String(), "enabled") {
		return true
	}
	return false
}

func defaultAPIKeyBetaHeader(body []byte) string {
	modelID := gjson.GetBytes(body, "model").String()
	if strings.Contains(strings.ToLower(modelID), "haiku") {
		return claude.APIKeyHaikuBetaHeader
	}
	return claude.APIKeyBetaHeader
}

func applyClaudeOAuthHeaderDefaults(req *http.Request, isStream bool) {
	if req == nil {
		return
	}
	if req.Header.Get("accept") == "" {
		req.Header.Set("accept", "application/json")
	}
	for key, value := range claude.DefaultHeaders {
		if value == "" {
			continue
		}
		if req.Header.Get(key) == "" {
			req.Header.Set(key, value)
		}
	}
	if isStream && req.Header.Get("x-stainless-helper-method") == "" {
		req.Header.Set("x-stainless-helper-method", "stream")
	}
}

func mergeAnthropicBeta(required []string, incoming string) string {
	seen := make(map[string]struct{}, len(required)+8)
	out := make([]string, 0, len(required)+8)

	add := func(v string) {
		v = strings.TrimSpace(v)
		if v == "" {
			return
		}
		if _, ok := seen[v]; ok {
			return
		}
		seen[v] = struct{}{}
		out = append(out, v)
	}

	for _, r := range required {
		add(r)
	}
	for _, p := range strings.Split(incoming, ",") {
		add(p)
	}
	return strings.Join(out, ",")
}

func mergeAnthropicBetaDropping(required []string, incoming string, drop map[string]struct{}) string {
	merged := mergeAnthropicBeta(required, incoming)
	if merged == "" || len(drop) == 0 {
		return merged
	}
	out := make([]string, 0, 8)
	for _, p := range strings.Split(merged, ",") {
		p = strings.TrimSpace(p)
		if p == "" {
			continue
		}
		if _, ok := drop[p]; ok {
			continue
		}
		out = append(out, p)
	}
	return strings.Join(out, ",")
}

// applyClaudeCodeMimicHeaders forces "Claude Code-like" request headers.
// This mirrors opencode-anthropic-auth behavior: do not trust downstream
// headers when using Claude Code-scoped OAuth credentials.
func applyClaudeCodeMimicHeaders(req *http.Request, isStream bool) {
	if req == nil {
		return
	}
	// Start with the standard defaults (fill missing).
	applyClaudeOAuthHeaderDefaults(req, isStream)
	// Then force key headers to match Claude Code fingerprint regardless of what the client sent.
	for key, value := range claude.DefaultHeaders {
		if value == "" {
			continue
		}
		req.Header.Set(key, value)
	}
	// Real Claude CLI uses Accept: application/json (even for streaming).
	req.Header.Set("accept", "application/json")
	if isStream {
		req.Header.Set("x-stainless-helper-method", "stream")
	}
}

func truncateForLog(b []byte, maxBytes int) string {
	if maxBytes <= 0 {
		maxBytes = 2048
	}
	if len(b) > maxBytes {
		b = b[:maxBytes]
	}
	s := string(b)
	// 保持一行，避免污染日志格式
	s = strings.ReplaceAll(s, "\n", "\\n")
	s = strings.ReplaceAll(s, "\r", "\\r")
	return s
}

// isThinkingBlockSignatureError 检测是否是thinking block相关错误
// 这类错误可以通过过滤thinking blocks并重试来解决
func (s *GatewayService) isThinkingBlockSignatureError(respBody []byte) bool {
	msg := strings.ToLower(strings.TrimSpace(extractUpstreamErrorMessage(respBody)))
	if msg == "" {
		return false
	}

	// Log for debugging
	log.Printf("[SignatureCheck] Checking error message: %s", msg)

	// 检测signature相关的错误（更宽松的匹配）
	// 例如: "Invalid `signature` in `thinking` block", "***.signature" 等
	if strings.Contains(msg, "signature") {
		log.Printf("[SignatureCheck] Detected signature error")
		return true
	}

	// 检测 thinking block 顺序/类型错误
	// 例如: "Expected `thinking` or `redacted_thinking`, but found `text`"
	if strings.Contains(msg, "expected") && (strings.Contains(msg, "thinking") || strings.Contains(msg, "redacted_thinking")) {
		log.Printf("[SignatureCheck] Detected thinking block type error")
		return true
	}

	// 检测 thinking block 被修改的错误
	// 例如: "thinking or redacted_thinking blocks in the latest assistant message cannot be modified"
	if strings.Contains(msg, "cannot be modified") && (strings.Contains(msg, "thinking") || strings.Contains(msg, "redacted_thinking")) {
		log.Printf("[SignatureCheck] Detected thinking block modification error")
		return true
	}

	// 检测空消息内容错误（可能是过滤 thinking blocks 后导致的）
	// 例如: "all messages must have non-empty content"
	if strings.Contains(msg, "non-empty content") || strings.Contains(msg, "empty content") {
		log.Printf("[SignatureCheck] Detected empty content error")
		return true
	}

	return false
}

func (s *GatewayService) shouldFailoverOn400(respBody []byte) bool {
	// 只对“可能是兼容性差异导致”的 400 允许切换，避免无意义重试。
	// 默认保守：无法识别则不切换。
	msg := strings.ToLower(strings.TrimSpace(extractUpstreamErrorMessage(respBody)))
	if msg == "" {
		return false
	}

	// 缺少/错误的 beta header：换账号/链路可能成功（尤其是混合调度时）。
	// 更精确匹配 beta 相关的兼容性问题，避免误触发切换。
	if strings.Contains(msg, "anthropic-beta") ||
		strings.Contains(msg, "beta feature") ||
		strings.Contains(msg, "requires beta") {
		return true
	}

	// thinking/tool streaming 等兼容性约束（常见于中间转换链路）
	if strings.Contains(msg, "thinking") || strings.Contains(msg, "thought_signature") || strings.Contains(msg, "signature") {
		return true
	}
	if strings.Contains(msg, "tool_use") || strings.Contains(msg, "tool_result") || strings.Contains(msg, "tools") {
		return true
	}

	return false
}

// ExtractUpstreamErrorMessage 从上游响应体中提取错误消息
// 支持 Claude 风格的错误格式：{"type":"error","error":{"type":"...","message":"..."}}
func ExtractUpstreamErrorMessage(body []byte) string {
	return extractUpstreamErrorMessage(body)
}

func extractUpstreamErrorMessage(body []byte) string {
	// Claude 风格：{"type":"error","error":{"type":"...","message":"..."}}
	if m := gjson.GetBytes(body, "error.message").String(); strings.TrimSpace(m) != "" {
		inner := strings.TrimSpace(m)
		// 有些上游会把完整 JSON 作为字符串塞进 message
		if strings.HasPrefix(inner, "{") {
			if innerMsg := gjson.Get(inner, "error.message").String(); strings.TrimSpace(innerMsg) != "" {
				return innerMsg
			}
		}
		return m
	}

	// 兜底：尝试顶层 message
	return gjson.GetBytes(body, "message").String()
}

func (s *GatewayService) handleErrorResponse(ctx context.Context, resp *http.Response, c *gin.Context, account *Account) (*ForwardResult, error) {
	body, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))

	// 调试日志：打印上游错误响应
	log.Printf("[Forward] Upstream error (non-retryable): Account=%d(%s) Status=%d RequestID=%s Body=%s",
		account.ID, account.Name, resp.StatusCode, resp.Header.Get("x-request-id"), truncateString(string(body), 1000))

	upstreamMsg := strings.TrimSpace(extractUpstreamErrorMessage(body))
	upstreamMsg = sanitizeUpstreamErrorMessage(upstreamMsg)

	// Print a compact upstream request fingerprint when we hit the Claude Code OAuth
	// credential scope error. This avoids requiring env-var tweaks in a fixed deploy.
	if isClaudeCodeCredentialScopeError(upstreamMsg) && c != nil {
		if v, ok := c.Get(claudeMimicDebugInfoKey); ok {
			if line, ok := v.(string); ok && strings.TrimSpace(line) != "" {
				log.Printf("[ClaudeMimicDebugOnError] status=%d request_id=%s %s",
					resp.StatusCode,
					resp.Header.Get("x-request-id"),
					line,
				)
			}
		}
	}

	// Enrich Ops error logs with upstream status + message, and optionally a truncated body snippet.
	upstreamDetail := ""
	if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
		maxBytes := s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes
		if maxBytes <= 0 {
			maxBytes = 2048
		}
		upstreamDetail = truncateString(string(body), maxBytes)
	}
	setOpsUpstreamError(c, resp.StatusCode, upstreamMsg, upstreamDetail)
	appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
		Platform:           account.Platform,
		AccountID:          account.ID,
		UpstreamStatusCode: resp.StatusCode,
		UpstreamRequestID:  resp.Header.Get("x-request-id"),
		Kind:               "http_error",
		Message:            upstreamMsg,
		Detail:             upstreamDetail,
	})

	// 处理上游错误，标记账号状态
	shouldDisable := false
	if s.rateLimitService != nil {
		shouldDisable = s.rateLimitService.HandleUpstreamError(ctx, account, resp.StatusCode, resp.Header, body)
	}
	if shouldDisable {
		return nil, &UpstreamFailoverError{StatusCode: resp.StatusCode, ResponseBody: body}
	}

	// 记录上游错误响应体摘要便于排障（可选：由配置控制；不回显到客户端）
	if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
		log.Printf(
			"Upstream error %d (account=%d platform=%s type=%s): %s",
			resp.StatusCode,
			account.ID,
			account.Platform,
			account.Type,
			truncateForLog(body, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes),
		)
	}

	// 非 failover 错误也支持错误透传规则匹配。
	if status, errType, errMsg, matched := applyErrorPassthroughRule(
		c,
		account.Platform,
		resp.StatusCode,
		body,
		http.StatusBadGateway,
		"upstream_error",
		"Upstream request failed",
	); matched {
		c.JSON(status, gin.H{
			"type": "error",
			"error": gin.H{
				"type":    errType,
				"message": errMsg,
			},
		})

		summary := upstreamMsg
		if summary == "" {
			summary = errMsg
		}
		if summary == "" {
			return nil, fmt.Errorf("upstream error: %d (passthrough rule matched)", resp.StatusCode)
		}
		return nil, fmt.Errorf("upstream error: %d (passthrough rule matched) message=%s", resp.StatusCode, summary)
	}

	// 根据状态码返回适当的自定义错误响应（不透传上游详细信息）
	var errType, errMsg string
	var statusCode int

	switch resp.StatusCode {
	case 400:
		c.Data(http.StatusBadRequest, "application/json", body)
		summary := upstreamMsg
		if summary == "" {
			summary = truncateForLog(body, 512)
		}
		if summary == "" {
			return nil, fmt.Errorf("upstream error: %d", resp.StatusCode)
		}
		return nil, fmt.Errorf("upstream error: %d message=%s", resp.StatusCode, summary)
	case 401:
		statusCode = http.StatusBadGateway
		errType = "upstream_error"
		errMsg = "Upstream authentication failed, please contact administrator"
	case 403:
		statusCode = http.StatusBadGateway
		errType = "upstream_error"
		errMsg = "Upstream access forbidden, please contact administrator"
	case 429:
		statusCode = http.StatusTooManyRequests
		errType = "rate_limit_error"
		errMsg = "Upstream rate limit exceeded, please retry later"
	case 529:
		statusCode = http.StatusServiceUnavailable
		errType = "overloaded_error"
		errMsg = "Upstream service overloaded, please retry later"
	case 500, 502, 503, 504:
		statusCode = http.StatusBadGateway
		errType = "upstream_error"
		errMsg = "Upstream service temporarily unavailable"
	default:
		statusCode = http.StatusBadGateway
		errType = "upstream_error"
		errMsg = "Upstream request failed"
	}

	// 返回自定义错误响应
	c.JSON(statusCode, gin.H{
		"type": "error",
		"error": gin.H{
			"type":    errType,
			"message": errMsg,
		},
	})

	if upstreamMsg == "" {
		return nil, fmt.Errorf("upstream error: %d", resp.StatusCode)
	}
	return nil, fmt.Errorf("upstream error: %d message=%s", resp.StatusCode, upstreamMsg)
}

func (s *GatewayService) handleRetryExhaustedSideEffects(ctx context.Context, resp *http.Response, account *Account) {
	body, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
	statusCode := resp.StatusCode

	// OAuth/Setup Token 账号的 403：标记账号异常
	if account.IsOAuth() && statusCode == 403 {
		s.rateLimitService.HandleUpstreamError(ctx, account, statusCode, resp.Header, body)
		log.Printf("Account %d: marked as error after %d retries for status %d", account.ID, maxRetryAttempts, statusCode)
	} else {
		// API Key 未配置错误码：不标记账号状态
		log.Printf("Account %d: upstream error %d after %d retries (not marking account)", account.ID, statusCode, maxRetryAttempts)
	}
}

func (s *GatewayService) handleFailoverSideEffects(ctx context.Context, resp *http.Response, account *Account) {
	body, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
	s.rateLimitService.HandleUpstreamError(ctx, account, resp.StatusCode, resp.Header, body)
}

// handleRetryExhaustedError 处理重试耗尽后的错误
// OAuth 403：标记账号异常
// API Key 未配置错误码：仅返回错误，不标记账号
func (s *GatewayService) handleRetryExhaustedError(ctx context.Context, resp *http.Response, c *gin.Context, account *Account) (*ForwardResult, error) {
	// Capture upstream error body before side-effects consume the stream.
	respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
	_ = resp.Body.Close()
	resp.Body = io.NopCloser(bytes.NewReader(respBody))

	s.handleRetryExhaustedSideEffects(ctx, resp, account)

	upstreamMsg := strings.TrimSpace(extractUpstreamErrorMessage(respBody))
	upstreamMsg = sanitizeUpstreamErrorMessage(upstreamMsg)

	if isClaudeCodeCredentialScopeError(upstreamMsg) && c != nil {
		if v, ok := c.Get(claudeMimicDebugInfoKey); ok {
			if line, ok := v.(string); ok && strings.TrimSpace(line) != "" {
				log.Printf("[ClaudeMimicDebugOnError] status=%d request_id=%s %s",
					resp.StatusCode,
					resp.Header.Get("x-request-id"),
					line,
				)
			}
		}
	}

	upstreamDetail := ""
	if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
		maxBytes := s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes
		if maxBytes <= 0 {
			maxBytes = 2048
		}
		upstreamDetail = truncateString(string(respBody), maxBytes)
	}
	setOpsUpstreamError(c, resp.StatusCode, upstreamMsg, upstreamDetail)
	appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
		Platform:           account.Platform,
		AccountID:          account.ID,
		UpstreamStatusCode: resp.StatusCode,
		UpstreamRequestID:  resp.Header.Get("x-request-id"),
		Kind:               "retry_exhausted",
		Message:            upstreamMsg,
		Detail:             upstreamDetail,
	})

	if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
		log.Printf(
			"Upstream error %d retries_exhausted (account=%d platform=%s type=%s): %s",
			resp.StatusCode,
			account.ID,
			account.Platform,
			account.Type,
			truncateForLog(respBody, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes),
		)
	}

	if status, errType, errMsg, matched := applyErrorPassthroughRule(
		c,
		account.Platform,
		resp.StatusCode,
		respBody,
		http.StatusBadGateway,
		"upstream_error",
		"Upstream request failed after retries",
	); matched {
		c.JSON(status, gin.H{
			"type": "error",
			"error": gin.H{
				"type":    errType,
				"message": errMsg,
			},
		})

		summary := upstreamMsg
		if summary == "" {
			summary = errMsg
		}
		if summary == "" {
			return nil, fmt.Errorf("upstream error: %d (retries exhausted, passthrough rule matched)", resp.StatusCode)
		}
		return nil, fmt.Errorf("upstream error: %d (retries exhausted, passthrough rule matched) message=%s", resp.StatusCode, summary)
	}

	// 返回统一的重试耗尽错误响应
	c.JSON(http.StatusBadGateway, gin.H{
		"type": "error",
		"error": gin.H{
			"type":    "upstream_error",
			"message": "Upstream request failed after retries",
		},
	})

	if upstreamMsg == "" {
		return nil, fmt.Errorf("upstream error: %d (retries exhausted)", resp.StatusCode)
	}
	return nil, fmt.Errorf("upstream error: %d (retries exhausted) message=%s", resp.StatusCode, upstreamMsg)
}

// streamingResult 流式响应结果
type streamingResult struct {
	usage            *ClaudeUsage
	firstTokenMs     *int
	clientDisconnect bool // 客户端是否在流式传输过程中断开
}

func (s *GatewayService) handleStreamingResponse(ctx context.Context, resp *http.Response, c *gin.Context, account *Account, startTime time.Time, originalModel, mappedModel string, mimicClaudeCode bool) (*streamingResult, error) {
	// 更新5h窗口状态
	s.rateLimitService.UpdateSessionWindow(ctx, account, resp.Header)

	if s.cfg != nil {
		responseheaders.WriteFilteredHeaders(c.Writer.Header(), resp.Header, s.cfg.Security.ResponseHeaders)
	}

	// 设置SSE响应头
	c.Header("Content-Type", "text/event-stream")
	c.Header("Cache-Control", "no-cache")
	c.Header("Connection", "keep-alive")
	c.Header("X-Accel-Buffering", "no")

	// 透传其他响应头
	if v := resp.Header.Get("x-request-id"); v != "" {
		c.Header("x-request-id", v)
	}

	w := c.Writer
	flusher, ok := w.(http.Flusher)
	if !ok {
		return nil, errors.New("streaming not supported")
	}

	usage := &ClaudeUsage{}
	var firstTokenMs *int
	scanner := bufio.NewScanner(resp.Body)
	// 设置更大的buffer以处理长行
	maxLineSize := defaultMaxLineSize
	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
		maxLineSize = s.cfg.Gateway.MaxLineSize
	}
	scanBuf := getSSEScannerBuf64K()
	scanner.Buffer(scanBuf[:0], maxLineSize)

	type scanEvent struct {
		line string
		err  error
	}
	// 独立 goroutine 读取上游，避免读取阻塞导致超时/keepalive无法处理
	events := make(chan scanEvent, 16)
	done := make(chan struct{})
	sendEvent := func(ev scanEvent) bool {
		select {
		case events <- ev:
			return true
		case <-done:
			return false
		}
	}
	var lastReadAt int64
	atomic.StoreInt64(&lastReadAt, time.Now().UnixNano())
	go func(scanBuf *sseScannerBuf64K) {
		defer putSSEScannerBuf64K(scanBuf)
		defer close(events)
		for scanner.Scan() {
			atomic.StoreInt64(&lastReadAt, time.Now().UnixNano())
			if !sendEvent(scanEvent{line: scanner.Text()}) {
				return
			}
		}
		if err := scanner.Err(); err != nil {
			_ = sendEvent(scanEvent{err: err})
		}
	}(scanBuf)
	defer close(done)

	streamInterval := time.Duration(0)
	if s.cfg != nil && s.cfg.Gateway.StreamDataIntervalTimeout > 0 {
		streamInterval = time.Duration(s.cfg.Gateway.StreamDataIntervalTimeout) * time.Second
	}
	// 仅监控上游数据间隔超时，避免下游写入阻塞导致误判
	var intervalTicker *time.Ticker
	if streamInterval > 0 {
		intervalTicker = time.NewTicker(streamInterval)
		defer intervalTicker.Stop()
	}
	var intervalCh <-chan time.Time
	if intervalTicker != nil {
		intervalCh = intervalTicker.C
	}

	// 仅发送一次错误事件，避免多次写入导致协议混乱（写失败时尽力通知客户端）
	errorEventSent := false
	sendErrorEvent := func(reason string) {
		if errorEventSent {
			return
		}
		errorEventSent = true
		_, _ = fmt.Fprintf(w, "event: error\ndata: {\"error\":\"%s\"}\n\n", reason)
		flusher.Flush()
	}

	needModelReplace := originalModel != mappedModel
	clientDisconnected := false // 客户端断开标志，断开后继续读取上游以获取完整usage

	pendingEventLines := make([]string, 0, 4)

	processSSEEvent := func(lines []string) ([]string, string, error) {
		if len(lines) == 0 {
			return nil, "", nil
		}

		eventName := ""
		dataLine := ""
		for _, line := range lines {
			trimmed := strings.TrimSpace(line)
			if strings.HasPrefix(trimmed, "event:") {
				eventName = strings.TrimSpace(strings.TrimPrefix(trimmed, "event:"))
				continue
			}
			if dataLine == "" && sseDataRe.MatchString(trimmed) {
				dataLine = sseDataRe.ReplaceAllString(trimmed, "")
			}
		}

		if eventName == "error" {
			return nil, dataLine, errors.New("have error in stream")
		}

		if dataLine == "" {
			return []string{strings.Join(lines, "\n") + "\n\n"}, "", nil
		}

		if dataLine == "[DONE]" {
			block := ""
			if eventName != "" {
				block = "event: " + eventName + "\n"
			}
			block += "data: " + dataLine + "\n\n"
			return []string{block}, dataLine, nil
		}

		var event map[string]any
		if err := json.Unmarshal([]byte(dataLine), &event); err != nil {
			// JSON 解析失败，直接透传原始数据
			block := ""
			if eventName != "" {
				block = "event: " + eventName + "\n"
			}
			block += "data: " + dataLine + "\n\n"
			return []string{block}, dataLine, nil
		}

		eventType, _ := event["type"].(string)
		if eventName == "" {
			eventName = eventType
		}

		// 兼容 Kimi cached_tokens → cache_read_input_tokens
		if eventType == "message_start" {
			if msg, ok := event["message"].(map[string]any); ok {
				if u, ok := msg["usage"].(map[string]any); ok {
					reconcileCachedTokens(u)
				}
			}
		}
		if eventType == "message_delta" {
			if u, ok := event["usage"].(map[string]any); ok {
				reconcileCachedTokens(u)
			}
		}

		if needModelReplace {
			if msg, ok := event["message"].(map[string]any); ok {
				if model, ok := msg["model"].(string); ok && model == mappedModel {
					msg["model"] = originalModel
				}
			}
		}

		newData, err := json.Marshal(event)
		if err != nil {
			// 序列化失败，直接透传原始数据
			block := ""
			if eventName != "" {
				block = "event: " + eventName + "\n"
			}
			block += "data: " + dataLine + "\n\n"
			return []string{block}, dataLine, nil
		}

		block := ""
		if eventName != "" {
			block = "event: " + eventName + "\n"
		}
		block += "data: " + string(newData) + "\n\n"
		return []string{block}, string(newData), nil
	}

	for {
		select {
		case ev, ok := <-events:
			if !ok {
				// 上游完成，返回结果
				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: clientDisconnected}, nil
			}
			if ev.err != nil {
				// 检测 context 取消（客户端断开会导致 context 取消，进而影响上游读取）
				if errors.Is(ev.err, context.Canceled) || errors.Is(ev.err, context.DeadlineExceeded) {
					log.Printf("Context canceled during streaming, returning collected usage")
					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
				}
				// 客户端已通过写入失败检测到断开，上游也出错了，返回已收集的 usage
				if clientDisconnected {
					log.Printf("Upstream read error after client disconnect: %v, returning collected usage", ev.err)
					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
				}
				// 客户端未断开，正常的错误处理
				if errors.Is(ev.err, bufio.ErrTooLong) {
					log.Printf("SSE line too long: account=%d max_size=%d error=%v", account.ID, maxLineSize, ev.err)
					sendErrorEvent("response_too_large")
					return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, ev.err
				}
				sendErrorEvent("stream_read_error")
				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream read error: %w", ev.err)
			}
			line := ev.line
			trimmed := strings.TrimSpace(line)

			if trimmed == "" {
				if len(pendingEventLines) == 0 {
					continue
				}

				outputBlocks, data, err := processSSEEvent(pendingEventLines)
				pendingEventLines = pendingEventLines[:0]
				if err != nil {
					if clientDisconnected {
						return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
					}
					return nil, err
				}

				for _, block := range outputBlocks {
					if !clientDisconnected {
						if _, werr := fmt.Fprint(w, block); werr != nil {
							clientDisconnected = true
							log.Printf("Client disconnected during streaming, continuing to drain upstream for billing")
							break
						}
						flusher.Flush()
					}
					if data != "" {
						if firstTokenMs == nil && data != "[DONE]" {
							ms := int(time.Since(startTime).Milliseconds())
							firstTokenMs = &ms
						}
						s.parseSSEUsage(data, usage)
					}
				}
				continue
			}

			pendingEventLines = append(pendingEventLines, line)

		case <-intervalCh:
			lastRead := time.Unix(0, atomic.LoadInt64(&lastReadAt))
			if time.Since(lastRead) < streamInterval {
				continue
			}
			if clientDisconnected {
				// 客户端已断开，上游也超时了，返回已收集的 usage
				log.Printf("Upstream timeout after client disconnect, returning collected usage")
				return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
			}
			log.Printf("Stream data interval timeout: account=%d model=%s interval=%s", account.ID, originalModel, streamInterval)
			// 处理流超时，可能标记账户为临时不可调度或错误状态
			if s.rateLimitService != nil {
				s.rateLimitService.HandleStreamTimeout(ctx, account, originalModel)
			}
			sendErrorEvent("stream_timeout")
			return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream data interval timeout")
		}
	}

}

func (s *GatewayService) parseSSEUsage(data string, usage *ClaudeUsage) {
	// 解析message_start获取input tokens（标准Claude API格式）
	var msgStart struct {
		Type    string `json:"type"`
		Message struct {
			Usage ClaudeUsage `json:"usage"`
		} `json:"message"`
	}
	if json.Unmarshal([]byte(data), &msgStart) == nil && msgStart.Type == "message_start" {
		usage.InputTokens = msgStart.Message.Usage.InputTokens
		usage.CacheCreationInputTokens = msgStart.Message.Usage.CacheCreationInputTokens
		usage.CacheReadInputTokens = msgStart.Message.Usage.CacheReadInputTokens
	}

	// 解析message_delta获取tokens（兼容GLM等把所有usage放在delta中的API）
	var msgDelta struct {
		Type  string `json:"type"`
		Usage struct {
			InputTokens              int `json:"input_tokens"`
			OutputTokens             int `json:"output_tokens"`
			CacheCreationInputTokens int `json:"cache_creation_input_tokens"`
			CacheReadInputTokens     int `json:"cache_read_input_tokens"`
		} `json:"usage"`
	}
	if json.Unmarshal([]byte(data), &msgDelta) == nil && msgDelta.Type == "message_delta" {
		// message_delta 仅覆盖存在且非0的字段
		// 避免覆盖 message_start 中已有的值（如 input_tokens）
		// Claude API 的 message_delta 通常只包含 output_tokens
		if msgDelta.Usage.InputTokens > 0 {
			usage.InputTokens = msgDelta.Usage.InputTokens
		}
		if msgDelta.Usage.OutputTokens > 0 {
			usage.OutputTokens = msgDelta.Usage.OutputTokens
		}
		if msgDelta.Usage.CacheCreationInputTokens > 0 {
			usage.CacheCreationInputTokens = msgDelta.Usage.CacheCreationInputTokens
		}
		if msgDelta.Usage.CacheReadInputTokens > 0 {
			usage.CacheReadInputTokens = msgDelta.Usage.CacheReadInputTokens
		}
	}
}

func (s *GatewayService) handleNonStreamingResponse(ctx context.Context, resp *http.Response, c *gin.Context, account *Account, originalModel, mappedModel string) (*ClaudeUsage, error) {
	// 更新5h窗口状态
	s.rateLimitService.UpdateSessionWindow(ctx, account, resp.Header)

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}

	// 解析usage
	var response struct {
		Usage ClaudeUsage `json:"usage"`
	}
	if err := json.Unmarshal(body, &response); err != nil {
		return nil, fmt.Errorf("parse response: %w", err)
	}

	// 兼容 Kimi cached_tokens → cache_read_input_tokens
	if response.Usage.CacheReadInputTokens == 0 {
		cachedTokens := gjson.GetBytes(body, "usage.cached_tokens").Int()
		if cachedTokens > 0 {
			response.Usage.CacheReadInputTokens = int(cachedTokens)
			if newBody, err := sjson.SetBytes(body, "usage.cache_read_input_tokens", cachedTokens); err == nil {
				body = newBody
			}
		}
	}

	// 如果有模型映射，替换响应中的model字段
	if originalModel != mappedModel {
		body = s.replaceModelInResponseBody(body, mappedModel, originalModel)
	}

	responseheaders.WriteFilteredHeaders(c.Writer.Header(), resp.Header, s.cfg.Security.ResponseHeaders)

	contentType := "application/json"
	if s.cfg != nil && !s.cfg.Security.ResponseHeaders.Enabled {
		if upstreamType := resp.Header.Get("Content-Type"); upstreamType != "" {
			contentType = upstreamType
		}
	}

	// 写入响应
	c.Data(resp.StatusCode, contentType, body)

	return &response.Usage, nil
}

// replaceModelInResponseBody 替换响应体中的model字段
// 使用 gjson/sjson 精确替换，避免全量 JSON 反序列化
func (s *GatewayService) replaceModelInResponseBody(body []byte, fromModel, toModel string) []byte {
	if m := gjson.GetBytes(body, "model"); m.Exists() && m.Str == fromModel {
		newBody, err := sjson.SetBytes(body, "model", toModel)
		if err != nil {
			return body
		}
		return newBody
	}
	return body
}

// RecordUsageInput 记录使用量的输入参数
type RecordUsageInput struct {
	Result            *ForwardResult
	APIKey            *APIKey
	User              *User
	Account           *Account
	Subscription      *UserSubscription  // 可选：订阅信息
	UserAgent         string             // 请求的 User-Agent
	IPAddress         string             // 请求的客户端 IP 地址
	ForceCacheBilling bool               // 强制缓存计费：将 input_tokens 转为 cache_read 计费（用于粘性会话切换）
	APIKeyService     APIKeyQuotaUpdater // 可选：用于更新API Key配额
}

// APIKeyQuotaUpdater defines the interface for updating API Key quota
type APIKeyQuotaUpdater interface {
	UpdateQuotaUsed(ctx context.Context, apiKeyID int64, cost float64) error
}

// RecordUsage 记录使用量并扣费（或更新订阅用量）
func (s *GatewayService) RecordUsage(ctx context.Context, input *RecordUsageInput) error {
	result := input.Result
	apiKey := input.APIKey
	user := input.User
	account := input.Account
	subscription := input.Subscription

	// 强制缓存计费：将 input_tokens 转为 cache_read_input_tokens
	// 用于粘性会话切换时的特殊计费处理
	if input.ForceCacheBilling && result.Usage.InputTokens > 0 {
		log.Printf("force_cache_billing: %d input_tokens → cache_read_input_tokens (account=%d)",
			result.Usage.InputTokens, account.ID)
		result.Usage.CacheReadInputTokens += result.Usage.InputTokens
		result.Usage.InputTokens = 0
	}

	// 获取费率倍数（优先级：用户专属 > 分组默认 > 系统默认）
	multiplier := s.cfg.Default.RateMultiplier
	if apiKey.GroupID != nil && apiKey.Group != nil {
		multiplier = apiKey.Group.RateMultiplier

		// 检查用户专属倍率
		if s.userGroupRateRepo != nil {
			if userRate, err := s.userGroupRateRepo.GetByUserAndGroup(ctx, user.ID, *apiKey.GroupID); err == nil && userRate != nil {
				multiplier = *userRate
			}
		}
	}

	var cost *CostBreakdown

	// 根据请求类型选择计费方式
	if result.MediaType == "image" || result.MediaType == "video" {
		var soraConfig *SoraPriceConfig
		if apiKey.Group != nil {
			soraConfig = &SoraPriceConfig{
				ImagePrice360:          apiKey.Group.SoraImagePrice360,
				ImagePrice540:          apiKey.Group.SoraImagePrice540,
				VideoPricePerRequest:   apiKey.Group.SoraVideoPricePerRequest,
				VideoPricePerRequestHD: apiKey.Group.SoraVideoPricePerRequestHD,
			}
		}
		if result.MediaType == "image" {
			cost = s.billingService.CalculateSoraImageCost(result.ImageSize, result.ImageCount, soraConfig, multiplier)
		} else {
			cost = s.billingService.CalculateSoraVideoCost(result.Model, soraConfig, multiplier)
		}
	} else if result.MediaType == "prompt" {
		cost = &CostBreakdown{}
	} else if result.ImageCount > 0 {
		// 图片生成计费
		var groupConfig *ImagePriceConfig
		if apiKey.Group != nil {
			groupConfig = &ImagePriceConfig{
				Price1K: apiKey.Group.ImagePrice1K,
				Price2K: apiKey.Group.ImagePrice2K,
				Price4K: apiKey.Group.ImagePrice4K,
			}
		}
		cost = s.billingService.CalculateImageCost(result.Model, result.ImageSize, result.ImageCount, groupConfig, multiplier)
	} else {
		// Token 计费
		tokens := UsageTokens{
			InputTokens:         result.Usage.InputTokens,
			OutputTokens:        result.Usage.OutputTokens,
			CacheCreationTokens: result.Usage.CacheCreationInputTokens,
			CacheReadTokens:     result.Usage.CacheReadInputTokens,
		}
		var err error
		cost, err = s.billingService.CalculateCost(result.Model, tokens, multiplier)
		if err != nil {
			log.Printf("Calculate cost failed: %v", err)
			cost = &CostBreakdown{ActualCost: 0}
		}
	}

	// 判断计费方式：订阅模式 vs 余额模式
	isSubscriptionBilling := subscription != nil && apiKey.Group != nil && apiKey.Group.IsSubscriptionType()
	billingType := BillingTypeBalance
	if isSubscriptionBilling {
		billingType = BillingTypeSubscription
	}

	// 创建使用日志
	durationMs := int(result.Duration.Milliseconds())
	var imageSize *string
	if result.ImageSize != "" {
		imageSize = &result.ImageSize
	}
	var mediaType *string
	if strings.TrimSpace(result.MediaType) != "" {
		mediaType = &result.MediaType
	}
	accountRateMultiplier := account.BillingRateMultiplier()
	usageLog := &UsageLog{
		UserID:                user.ID,
		APIKeyID:              apiKey.ID,
		AccountID:             account.ID,
		RequestID:             result.RequestID,
		Model:                 result.Model,
		InputTokens:           result.Usage.InputTokens,
		OutputTokens:          result.Usage.OutputTokens,
		CacheCreationTokens:   result.Usage.CacheCreationInputTokens,
		CacheReadTokens:       result.Usage.CacheReadInputTokens,
		InputCost:             cost.InputCost,
		OutputCost:            cost.OutputCost,
		CacheCreationCost:     cost.CacheCreationCost,
		CacheReadCost:         cost.CacheReadCost,
		TotalCost:             cost.TotalCost,
		ActualCost:            cost.ActualCost,
		RateMultiplier:        multiplier,
		AccountRateMultiplier: &accountRateMultiplier,
		BillingType:           billingType,
		Stream:                result.Stream,
		DurationMs:            &durationMs,
		FirstTokenMs:          result.FirstTokenMs,
		ImageCount:            result.ImageCount,
		ImageSize:             imageSize,
		MediaType:             mediaType,
		CreatedAt:             time.Now(),
	}

	// 添加 UserAgent
	if input.UserAgent != "" {
		usageLog.UserAgent = &input.UserAgent
	}

	// 添加 IPAddress
	if input.IPAddress != "" {
		usageLog.IPAddress = &input.IPAddress
	}

	// 添加分组和订阅关联
	if apiKey.GroupID != nil {
		usageLog.GroupID = apiKey.GroupID
	}
	if subscription != nil {
		usageLog.SubscriptionID = &subscription.ID
	}

	inserted, err := s.usageLogRepo.Create(ctx, usageLog)
	if err != nil {
		log.Printf("Create usage log failed: %v", err)
	}

	if s.cfg != nil && s.cfg.RunMode == config.RunModeSimple {
		log.Printf("[SIMPLE MODE] Usage recorded (not billed): user=%d, tokens=%d", usageLog.UserID, usageLog.TotalTokens())
		s.deferredService.ScheduleLastUsedUpdate(account.ID)
		return nil
	}

	shouldBill := inserted || err != nil

	// 根据计费类型执行扣费
	if isSubscriptionBilling {
		// 订阅模式：更新订阅用量（使用 TotalCost 原始费用，不考虑倍率）
		if shouldBill && cost.TotalCost > 0 {
			if err := s.userSubRepo.IncrementUsage(ctx, subscription.ID, cost.TotalCost); err != nil {
				log.Printf("Increment subscription usage failed: %v", err)
			}
			// 异步更新订阅缓存
			s.billingCacheService.QueueUpdateSubscriptionUsage(user.ID, *apiKey.GroupID, cost.TotalCost)
		}
	} else {
		// 余额模式：扣除用户余额（使用 ActualCost 考虑倍率后的费用）
		if shouldBill && cost.ActualCost > 0 {
			if err := s.userRepo.DeductBalance(ctx, user.ID, cost.ActualCost); err != nil {
				log.Printf("Deduct balance failed: %v", err)
			}
			// 异步更新余额缓存
			s.billingCacheService.QueueDeductBalance(user.ID, cost.ActualCost)
		}
	}

	// 更新 API Key 配额（如果设置了配额限制）
	if shouldBill && cost.ActualCost > 0 && apiKey.Quota > 0 && input.APIKeyService != nil {
		if err := input.APIKeyService.UpdateQuotaUsed(ctx, apiKey.ID, cost.ActualCost); err != nil {
			log.Printf("Update API key quota failed: %v", err)
		}
	}

	// Schedule batch update for account last_used_at
	s.deferredService.ScheduleLastUsedUpdate(account.ID)

	return nil
}

// RecordUsageLongContextInput 记录使用量的输入参数（支持长上下文双倍计费）
type RecordUsageLongContextInput struct {
	Result                *ForwardResult
	APIKey                *APIKey
	User                  *User
	Account               *Account
	Subscription          *UserSubscription // 可选：订阅信息
	UserAgent             string            // 请求的 User-Agent
	IPAddress             string            // 请求的客户端 IP 地址
	LongContextThreshold  int               // 长上下文阈值（如 200000）
	LongContextMultiplier float64           // 超出阈值部分的倍率（如 2.0）
	ForceCacheBilling     bool              // 强制缓存计费：将 input_tokens 转为 cache_read 计费（用于粘性会话切换）
	APIKeyService         *APIKeyService    // API Key 配额服务（可选）
}

// RecordUsageWithLongContext 记录使用量并扣费，支持长上下文双倍计费（用于 Gemini）
func (s *GatewayService) RecordUsageWithLongContext(ctx context.Context, input *RecordUsageLongContextInput) error {
	result := input.Result
	apiKey := input.APIKey
	user := input.User
	account := input.Account
	subscription := input.Subscription

	// 强制缓存计费：将 input_tokens 转为 cache_read_input_tokens
	// 用于粘性会话切换时的特殊计费处理
	if input.ForceCacheBilling && result.Usage.InputTokens > 0 {
		log.Printf("force_cache_billing: %d input_tokens → cache_read_input_tokens (account=%d)",
			result.Usage.InputTokens, account.ID)
		result.Usage.CacheReadInputTokens += result.Usage.InputTokens
		result.Usage.InputTokens = 0
	}

	// 获取费率倍数（优先级：用户专属 > 分组默认 > 系统默认）
	multiplier := s.cfg.Default.RateMultiplier
	if apiKey.GroupID != nil && apiKey.Group != nil {
		multiplier = apiKey.Group.RateMultiplier

		// 检查用户专属倍率
		if s.userGroupRateRepo != nil {
			if userRate, err := s.userGroupRateRepo.GetByUserAndGroup(ctx, user.ID, *apiKey.GroupID); err == nil && userRate != nil {
				multiplier = *userRate
			}
		}
	}

	var cost *CostBreakdown

	// 根据请求类型选择计费方式
	if result.ImageCount > 0 {
		// 图片生成计费
		var groupConfig *ImagePriceConfig
		if apiKey.Group != nil {
			groupConfig = &ImagePriceConfig{
				Price1K: apiKey.Group.ImagePrice1K,
				Price2K: apiKey.Group.ImagePrice2K,
				Price4K: apiKey.Group.ImagePrice4K,
			}
		}
		cost = s.billingService.CalculateImageCost(result.Model, result.ImageSize, result.ImageCount, groupConfig, multiplier)
	} else {
		// Token 计费（使用长上下文计费方法）
		tokens := UsageTokens{
			InputTokens:         result.Usage.InputTokens,
			OutputTokens:        result.Usage.OutputTokens,
			CacheCreationTokens: result.Usage.CacheCreationInputTokens,
			CacheReadTokens:     result.Usage.CacheReadInputTokens,
		}
		var err error
		cost, err = s.billingService.CalculateCostWithLongContext(result.Model, tokens, multiplier, input.LongContextThreshold, input.LongContextMultiplier)
		if err != nil {
			log.Printf("Calculate cost failed: %v", err)
			cost = &CostBreakdown{ActualCost: 0}
		}
	}

	// 判断计费方式：订阅模式 vs 余额模式
	isSubscriptionBilling := subscription != nil && apiKey.Group != nil && apiKey.Group.IsSubscriptionType()
	billingType := BillingTypeBalance
	if isSubscriptionBilling {
		billingType = BillingTypeSubscription
	}

	// 创建使用日志
	durationMs := int(result.Duration.Milliseconds())
	var imageSize *string
	if result.ImageSize != "" {
		imageSize = &result.ImageSize
	}
	accountRateMultiplier := account.BillingRateMultiplier()
	usageLog := &UsageLog{
		UserID:                user.ID,
		APIKeyID:              apiKey.ID,
		AccountID:             account.ID,
		RequestID:             result.RequestID,
		Model:                 result.Model,
		InputTokens:           result.Usage.InputTokens,
		OutputTokens:          result.Usage.OutputTokens,
		CacheCreationTokens:   result.Usage.CacheCreationInputTokens,
		CacheReadTokens:       result.Usage.CacheReadInputTokens,
		InputCost:             cost.InputCost,
		OutputCost:            cost.OutputCost,
		CacheCreationCost:     cost.CacheCreationCost,
		CacheReadCost:         cost.CacheReadCost,
		TotalCost:             cost.TotalCost,
		ActualCost:            cost.ActualCost,
		RateMultiplier:        multiplier,
		AccountRateMultiplier: &accountRateMultiplier,
		BillingType:           billingType,
		Stream:                result.Stream,
		DurationMs:            &durationMs,
		FirstTokenMs:          result.FirstTokenMs,
		ImageCount:            result.ImageCount,
		ImageSize:             imageSize,
		CreatedAt:             time.Now(),
	}

	// 添加 UserAgent
	if input.UserAgent != "" {
		usageLog.UserAgent = &input.UserAgent
	}

	// 添加 IPAddress
	if input.IPAddress != "" {
		usageLog.IPAddress = &input.IPAddress
	}

	// 添加分组和订阅关联
	if apiKey.GroupID != nil {
		usageLog.GroupID = apiKey.GroupID
	}
	if subscription != nil {
		usageLog.SubscriptionID = &subscription.ID
	}

	inserted, err := s.usageLogRepo.Create(ctx, usageLog)
	if err != nil {
		log.Printf("Create usage log failed: %v", err)
	}

	if s.cfg != nil && s.cfg.RunMode == config.RunModeSimple {
		log.Printf("[SIMPLE MODE] Usage recorded (not billed): user=%d, tokens=%d", usageLog.UserID, usageLog.TotalTokens())
		s.deferredService.ScheduleLastUsedUpdate(account.ID)
		return nil
	}

	shouldBill := inserted || err != nil

	// 根据计费类型执行扣费
	if isSubscriptionBilling {
		// 订阅模式：更新订阅用量（使用 TotalCost 原始费用，不考虑倍率）
		if shouldBill && cost.TotalCost > 0 {
			if err := s.userSubRepo.IncrementUsage(ctx, subscription.ID, cost.TotalCost); err != nil {
				log.Printf("Increment subscription usage failed: %v", err)
			}
			// 异步更新订阅缓存
			s.billingCacheService.QueueUpdateSubscriptionUsage(user.ID, *apiKey.GroupID, cost.TotalCost)
		}
	} else {
		// 余额模式：扣除用户余额（使用 ActualCost 考虑倍率后的费用）
		if shouldBill && cost.ActualCost > 0 {
			if err := s.userRepo.DeductBalance(ctx, user.ID, cost.ActualCost); err != nil {
				log.Printf("Deduct balance failed: %v", err)
			}
			// 异步更新余额缓存
			s.billingCacheService.QueueDeductBalance(user.ID, cost.ActualCost)
			// API Key 独立配额扣费
			if input.APIKeyService != nil && apiKey.Quota > 0 {
				if err := input.APIKeyService.UpdateQuotaUsed(ctx, apiKey.ID, cost.ActualCost); err != nil {
					log.Printf("Add API key quota used failed: %v", err)
				}
			}
		}
	}

	// Schedule batch update for account last_used_at
	s.deferredService.ScheduleLastUsedUpdate(account.ID)

	return nil
}

// ForwardCountTokens 转发 count_tokens 请求到上游 API
// 特点：不记录使用量、仅支持非流式响应
func (s *GatewayService) ForwardCountTokens(ctx context.Context, c *gin.Context, account *Account, parsed *ParsedRequest) error {
	if parsed == nil {
		s.countTokensError(c, http.StatusBadRequest, "invalid_request_error", "Request body is empty")
		return fmt.Errorf("parse request: empty request")
	}

	body := parsed.Body
	reqModel := parsed.Model

	isClaudeCode := isClaudeCodeRequest(ctx, c, parsed)
	shouldMimicClaudeCode := account.IsOAuth() && !isClaudeCode

	if shouldMimicClaudeCode {
		normalizeOpts := claudeOAuthNormalizeOptions{stripSystemCacheControl: true}
		body, reqModel = normalizeClaudeOAuthRequestBody(body, reqModel, normalizeOpts)
	}

	// Antigravity 账户不支持 count_tokens 转发，直接返回空值
	if account.Platform == PlatformAntigravity {
		c.JSON(http.StatusOK, gin.H{"input_tokens": 0})
		return nil
	}

	// 应用模型映射：
	// - APIKey 账号：使用账号级别的显式映射（如果配置），否则透传原始模型名
	// - OAuth/SetupToken 账号：使用 Anthropic 标准映射（短ID → 长ID）
	if reqModel != "" {
		mappedModel := reqModel
		mappingSource := ""
		if account.Type == AccountTypeAPIKey {
			mappedModel = account.GetMappedModel(reqModel)
			if mappedModel != reqModel {
				mappingSource = "account"
			}
		}
		if mappingSource == "" && account.Platform == PlatformAnthropic && account.Type != AccountTypeAPIKey {
			normalized := claude.NormalizeModelID(reqModel)
			if normalized != reqModel {
				mappedModel = normalized
				mappingSource = "prefix"
			}
		}
		if mappedModel != reqModel {
			body = s.replaceModelInBody(body, mappedModel)
			reqModel = mappedModel
			log.Printf("CountTokens model mapping applied: %s -> %s (account: %s, source=%s)", parsed.Model, mappedModel, account.Name, mappingSource)
		}
	}

	// 获取凭证
	token, tokenType, err := s.GetAccessToken(ctx, account)
	if err != nil {
		s.countTokensError(c, http.StatusBadGateway, "upstream_error", "Failed to get access token")
		return err
	}

	// 构建上游请求
	upstreamReq, err := s.buildCountTokensRequest(ctx, c, account, body, token, tokenType, reqModel, shouldMimicClaudeCode)
	if err != nil {
		s.countTokensError(c, http.StatusInternalServerError, "api_error", "Failed to build request")
		return err
	}

	// 获取代理URL
	proxyURL := ""
	if account.ProxyID != nil && account.Proxy != nil {
		proxyURL = account.Proxy.URL()
	}

	// 发送请求
	resp, err := s.httpUpstream.DoWithTLS(upstreamReq, proxyURL, account.ID, account.Concurrency, account.IsTLSFingerprintEnabled())
	if err != nil {
		setOpsUpstreamError(c, 0, sanitizeUpstreamErrorMessage(err.Error()), "")
		s.countTokensError(c, http.StatusBadGateway, "upstream_error", "Request failed")
		return fmt.Errorf("upstream request failed: %w", err)
	}

	// 读取响应体
	respBody, err := io.ReadAll(resp.Body)
	_ = resp.Body.Close()
	if err != nil {
		s.countTokensError(c, http.StatusBadGateway, "upstream_error", "Failed to read response")
		return err
	}

	// 检测 thinking block 签名错误（400）并重试一次（过滤 thinking blocks）
	if resp.StatusCode == 400 && s.isThinkingBlockSignatureError(respBody) {
		log.Printf("Account %d: detected thinking block signature error on count_tokens, retrying with filtered thinking blocks", account.ID)

		filteredBody := FilterThinkingBlocksForRetry(body)
		retryReq, buildErr := s.buildCountTokensRequest(ctx, c, account, filteredBody, token, tokenType, reqModel, shouldMimicClaudeCode)
		if buildErr == nil {
			retryResp, retryErr := s.httpUpstream.DoWithTLS(retryReq, proxyURL, account.ID, account.Concurrency, account.IsTLSFingerprintEnabled())
			if retryErr == nil {
				resp = retryResp
				respBody, err = io.ReadAll(resp.Body)
				_ = resp.Body.Close()
				if err != nil {
					s.countTokensError(c, http.StatusBadGateway, "upstream_error", "Failed to read response")
					return err
				}
			}
		}
	}

	// 处理错误响应
	if resp.StatusCode >= 400 {
		// 标记账号状态（429/529等）
		s.rateLimitService.HandleUpstreamError(ctx, account, resp.StatusCode, resp.Header, respBody)

		upstreamMsg := strings.TrimSpace(extractUpstreamErrorMessage(respBody))
		upstreamMsg = sanitizeUpstreamErrorMessage(upstreamMsg)
		upstreamDetail := ""
		if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
			maxBytes := s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes
			if maxBytes <= 0 {
				maxBytes = 2048
			}
			upstreamDetail = truncateString(string(respBody), maxBytes)
		}
		setOpsUpstreamError(c, resp.StatusCode, upstreamMsg, upstreamDetail)

		// 记录上游错误摘要便于排障（不回显请求内容）
		if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
			log.Printf(
				"count_tokens upstream error %d (account=%d platform=%s type=%s): %s",
				resp.StatusCode,
				account.ID,
				account.Platform,
				account.Type,
				truncateForLog(respBody, s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes),
			)
		}

		// 返回简化的错误响应
		errMsg := "Upstream request failed"
		switch resp.StatusCode {
		case 429:
			errMsg = "Rate limit exceeded"
		case 529:
			errMsg = "Service overloaded"
		}
		s.countTokensError(c, resp.StatusCode, "upstream_error", errMsg)
		if upstreamMsg == "" {
			return fmt.Errorf("upstream error: %d", resp.StatusCode)
		}
		return fmt.Errorf("upstream error: %d message=%s", resp.StatusCode, upstreamMsg)
	}

	// 透传成功响应
	c.Data(resp.StatusCode, "application/json", respBody)
	return nil
}

// buildCountTokensRequest 构建 count_tokens 上游请求
func (s *GatewayService) buildCountTokensRequest(ctx context.Context, c *gin.Context, account *Account, body []byte, token, tokenType, modelID string, mimicClaudeCode bool) (*http.Request, error) {
	// 确定目标 URL
	targetURL := claudeAPICountTokensURL
	if account.Type == AccountTypeAPIKey {
		baseURL := account.GetBaseURL()
		if baseURL != "" {
			validatedURL, err := s.validateUpstreamBaseURL(baseURL)
			if err != nil {
				return nil, err
			}
			targetURL = validatedURL + "/v1/messages/count_tokens"
		}
	}

	clientHeaders := http.Header{}
	if c != nil && c.Request != nil {
		clientHeaders = c.Request.Header
	}

	// OAuth 账号：应用统一指纹和重写 userID
	// 如果启用了会话ID伪装，会在重写后替换 session 部分为固定值
	if account.IsOAuth() && s.identityService != nil {
		fp, err := s.identityService.GetOrCreateFingerprint(ctx, account.ID, clientHeaders)
		if err == nil {
			accountUUID := account.GetExtraString("account_uuid")
			if accountUUID != "" && fp.ClientID != "" {
				if newBody, err := s.identityService.RewriteUserIDWithMasking(ctx, body, account, accountUUID, fp.ClientID); err == nil && len(newBody) > 0 {
					body = newBody
				}
			}
		}
	}

	req, err := http.NewRequestWithContext(ctx, "POST", targetURL, bytes.NewReader(body))
	if err != nil {
		return nil, err
	}

	// 设置认证头
	if tokenType == "oauth" {
		req.Header.Set("authorization", "Bearer "+token)
	} else {
		req.Header.Set("x-api-key", token)
	}

	// 白名单透传 headers
	for key, values := range clientHeaders {
		lowerKey := strings.ToLower(key)
		if allowedHeaders[lowerKey] {
			for _, v := range values {
				req.Header.Add(key, v)
			}
		}
	}

	// OAuth 账号：应用指纹到请求头
	if account.IsOAuth() && s.identityService != nil {
		fp, _ := s.identityService.GetOrCreateFingerprint(ctx, account.ID, clientHeaders)
		if fp != nil {
			s.identityService.ApplyFingerprint(req, fp)
		}
	}

	// 确保必要的 headers 存在
	if req.Header.Get("content-type") == "" {
		req.Header.Set("content-type", "application/json")
	}
	if req.Header.Get("anthropic-version") == "" {
		req.Header.Set("anthropic-version", "2023-06-01")
	}
	if tokenType == "oauth" {
		applyClaudeOAuthHeaderDefaults(req, false)
	}

	// OAuth 账号：处理 anthropic-beta header
	if tokenType == "oauth" {
		if mimicClaudeCode {
			applyClaudeCodeMimicHeaders(req, false)

			incomingBeta := req.Header.Get("anthropic-beta")
			requiredBetas := []string{claude.BetaClaudeCode, claude.BetaOAuth, claude.BetaInterleavedThinking, claude.BetaTokenCounting}
			req.Header.Set("anthropic-beta", mergeAnthropicBeta(requiredBetas, incomingBeta))
		} else {
			clientBetaHeader := req.Header.Get("anthropic-beta")
			if clientBetaHeader == "" {
				req.Header.Set("anthropic-beta", claude.CountTokensBetaHeader)
			} else {
				beta := s.getBetaHeader(modelID, clientBetaHeader)
				if !strings.Contains(beta, claude.BetaTokenCounting) {
					beta = beta + "," + claude.BetaTokenCounting
				}
				req.Header.Set("anthropic-beta", beta)
			}
		}
	} else if s.cfg != nil && s.cfg.Gateway.InjectBetaForAPIKey && req.Header.Get("anthropic-beta") == "" {
		// API-key：与 messages 同步的按需 beta 注入（默认关闭）
		if requestNeedsBetaFeatures(body) {
			if beta := defaultAPIKeyBetaHeader(body); beta != "" {
				req.Header.Set("anthropic-beta", beta)
			}
		}
	}

	if c != nil && tokenType == "oauth" {
		c.Set(claudeMimicDebugInfoKey, buildClaudeMimicDebugLine(req, body, account, tokenType, mimicClaudeCode))
	}
	if s.debugClaudeMimicEnabled() {
		logClaudeMimicDebug(req, body, account, tokenType, mimicClaudeCode)
	}

	return req, nil
}

// countTokensError 返回 count_tokens 错误响应
func (s *GatewayService) countTokensError(c *gin.Context, status int, errType, message string) {
	c.JSON(status, gin.H{
		"type": "error",
		"error": gin.H{
			"type":    errType,
			"message": message,
		},
	})
}

func (s *GatewayService) validateUpstreamBaseURL(raw string) (string, error) {
	if s.cfg != nil && !s.cfg.Security.URLAllowlist.Enabled {
		normalized, err := urlvalidator.ValidateURLFormat(raw, s.cfg.Security.URLAllowlist.AllowInsecureHTTP)
		if err != nil {
			return "", fmt.Errorf("invalid base_url: %w", err)
		}
		return normalized, nil
	}
	normalized, err := urlvalidator.ValidateHTTPSURL(raw, urlvalidator.ValidationOptions{
		AllowedHosts:     s.cfg.Security.URLAllowlist.UpstreamHosts,
		RequireAllowlist: true,
		AllowPrivate:     s.cfg.Security.URLAllowlist.AllowPrivateHosts,
	})
	if err != nil {
		return "", fmt.Errorf("invalid base_url: %w", err)
	}
	return normalized, nil
}

// checkAntigravityModelScope 检查 Antigravity 平台的模型系列是否在分组支持范围内
func (s *GatewayService) checkAntigravityModelScope(ctx context.Context, groupID int64, requestedModel string) error {
	scope, ok := ResolveAntigravityQuotaScope(requestedModel)
	if !ok {
		return nil // 无法解析 scope，跳过检查
	}

	group, err := s.resolveGroupByID(ctx, groupID)
	if err != nil {
		return nil // 查询失败时放行
	}
	if group == nil {
		return nil // 分组不存在时放行
	}

	if !IsScopeSupported(group.SupportedModelScopes, scope) {
		return ErrModelScopeNotSupported
	}
	return nil
}

// GetAvailableModels returns the list of models available for a group
// It aggregates model_mapping keys from all schedulable accounts in the group
func (s *GatewayService) GetAvailableModels(ctx context.Context, groupID *int64, platform string) []string {
	var accounts []Account
	var err error

	if groupID != nil {
		accounts, err = s.accountRepo.ListSchedulableByGroupID(ctx, *groupID)
	} else {
		accounts, err = s.accountRepo.ListSchedulable(ctx)
	}

	if err != nil || len(accounts) == 0 {
		return nil
	}

	// Filter by platform if specified
	if platform != "" {
		filtered := make([]Account, 0)
		for _, acc := range accounts {
			if acc.Platform == platform {
				filtered = append(filtered, acc)
			}
		}
		accounts = filtered
	}

	// Collect unique models from all accounts
	modelSet := make(map[string]struct{})
	hasAnyMapping := false

	for _, acc := range accounts {
		mapping := acc.GetModelMapping()
		if len(mapping) > 0 {
			hasAnyMapping = true
			for model := range mapping {
				modelSet[model] = struct{}{}
			}
		}
	}

	// If no account has model_mapping, return nil (use default)
	if !hasAnyMapping {
		return nil
	}

	// Convert to slice
	models := make([]string, 0, len(modelSet))
	for model := range modelSet {
		models = append(models, model)
	}

	return models
}

// reconcileCachedTokens 兼容 Kimi 等上游：
// 将 OpenAI 风格的 cached_tokens 映射到 Claude 标准的 cache_read_input_tokens
func reconcileCachedTokens(usage map[string]any) bool {
	if usage == nil {
		return false
	}
	cacheRead, _ := usage["cache_read_input_tokens"].(float64)
	if cacheRead > 0 {
		return false // 已有标准字段，无需处理
	}
	cached, _ := usage["cached_tokens"].(float64)
	if cached <= 0 {
		return false
	}
	usage["cache_read_input_tokens"] = cached
	return true
}
