实现支付商户池与微信授权配置

新增收款商户、商户池轮询、微信授权配置独立管理；三类新支付
（C端套餐购买、C端资产钱包充值、代理在线预存款充值）无条件
经商户池选择并冻结路由，无旧综合配置回退。merchant_id 为空
历史支付继续按 payment_config_id 双读。凭证版本化加载与
ID+版本缓存保证轮换一致性。删除商户池新支付创建开关及全部
引用。

internal/application/merchantpayment/management.go

@@ -0,0 +1,721 @@
+// Package merchantpayment provides merchant pool payment routing use cases.
+package merchantpayment
+
+import (
+	"context"
+	"reflect"
+	"strconv"
+	"strings"
+	"time"
+
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+
+	systemconfigapp "github.com/break/junhong_cmp_fiber/internal/application/systemconfig"
+
+	"github.com/break/junhong_cmp_fiber/internal/model"
+	"github.com/break/junhong_cmp_fiber/internal/model/dto"
+	"github.com/break/junhong_cmp_fiber/pkg/constants"
+	"github.com/break/junhong_cmp_fiber/pkg/errors"
+	"github.com/break/junhong_cmp_fiber/pkg/middleware"
+	"github.com/bytedance/sonic"
+)
+
+// ManagementService 负责商户、商户池与授权配置写入。
+type ManagementService struct {
+	db    *gorm.DB
+	audit systemconfigapp.AuditWriter
+}
+
+// NewManagementService 创建商户配置用例。
+func NewManagementService(db *gorm.DB, audit systemconfigapp.AuditWriter) *ManagementService {
+	return &ManagementService{db: db, audit: audit}
+}
+
+func requireManager(ctx context.Context) error {
+	kind := middleware.GetUserTypeFromContext(ctx)
+	if kind != constants.UserTypeSuperAdmin && kind != constants.UserTypePlatform {
+		return errors.New(errors.CodeForbidden, "无权限访问支付商户配置")
+	}
+	return nil
+}
+
+func normalizePage(page, size int) (int, int) {
+	if page < 1 {
+		page = 1
+	}
+	if size < 1 {
+		size = 20
+	}
+	if size > 100 {
+		size = 100
+	}
+	return page, size
+}
+
+func validPaymentMethod(method string) bool {
+	return method == "wechat" || method == "alipay"
+}
+
+func validateMerchantConfiguration(paymentMethod, providerType, merchantIdentity string, credentials model.JSONB) error {
+	paymentMethod, providerType, merchantIdentity = strings.TrimSpace(paymentMethod), strings.TrimSpace(providerType), strings.TrimSpace(merchantIdentity)
+	if !validPaymentMethod(paymentMethod) || merchantIdentity == "" || len(credentials) == 0 {
+		return errors.New(errors.CodeInvalidParam, "支付商户配置不完整")
+	}
+	var config model.WechatConfig
+	raw, err := sonic.Marshal(credentials)
+	if err != nil || sonic.Unmarshal(raw, &config) != nil {
+		return errors.New(errors.CodeInvalidParam, "支付商户凭证格式无效")
+	}
+	switch paymentMethod {
+	case "wechat":
+		switch providerType {
+		case model.ProviderTypeWechat:
+			if config.WxMchID != merchantIdentity || strings.TrimSpace(config.WxAPIV3Key) == "" || strings.TrimSpace(config.WxCertContent) == "" || strings.TrimSpace(config.WxKeyContent) == "" || strings.TrimSpace(config.WxSerialNo) == "" || strings.TrimSpace(config.WxNotifyURL) == "" {
+				return errors.New(errors.CodeInvalidParam, "微信直连商户凭证不完整或身份不一致")
+			}
+		case model.ProviderTypeWechatV2:
+			if config.WxMchID != merchantIdentity || strings.TrimSpace(config.WxAPIV2Key) == "" || strings.TrimSpace(config.WxNotifyURL) == "" {
+				return errors.New(errors.CodeInvalidParam, "微信 v2 商户凭证不完整或身份不一致")
+			}
+		case model.ProviderTypeFuiou:
+			if config.FyMchntCd != merchantIdentity || strings.TrimSpace(config.FyInsCd) == "" || strings.TrimSpace(config.FyTermID) == "" || strings.TrimSpace(config.FyPrivateKey) == "" || strings.TrimSpace(config.FyPublicKey) == "" || strings.TrimSpace(config.FyAPIURL) == "" || strings.TrimSpace(config.FyNotifyURL) == "" {
+				return errors.New(errors.CodeInvalidParam, "富友商户凭证不完整或身份不一致")
+			}
+		default:
+			return errors.New(errors.CodeInvalidParam, "微信支付服务商类型无效")
+		}
+	case "alipay":
+		if providerType != "alipay" || config.AliAppID != merchantIdentity || strings.TrimSpace(config.AliPrivateKey) == "" || strings.TrimSpace(config.AliPublicKey) == "" || strings.TrimSpace(config.AliNotifyURL) == "" || strings.TrimSpace(config.AliReturnURL) == "" {
+			return errors.New(errors.CodeInvalidParam, "支付宝商户凭证不完整或身份不一致")
+		}
+	}
+	return nil
+}
+
+func validatePoolRequest(req dto.PaymentMerchantPoolRequest) error {
+	if !validPaymentMethod(strings.TrimSpace(req.PaymentMethod)) {
+		return errors.New(errors.CodeInvalidParam, "支付方式仅支持微信或支付宝")
+	}
+	switch req.Strategy {
+	case model.PaymentMerchantStrategyAmount:
+		if req.ThresholdAmount == nil || *req.ThresholdAmount <= 0 || req.ThresholdCount != nil || req.StatisticCycle == nil || !validStatisticCycle(*req.StatisticCycle) || req.TimePeriodValue != nil || req.TimePeriodUnit != nil || req.TimePeriodStartedAt != nil {
+			return errors.New(errors.CodeInvalidParam, "金额轮询策略参数不完整")
+		}
+	case model.PaymentMerchantStrategyCount:
+		if req.ThresholdCount == nil || *req.ThresholdCount <= 0 || req.ThresholdAmount != nil || req.StatisticCycle == nil || !validStatisticCycle(*req.StatisticCycle) || req.TimePeriodValue != nil || req.TimePeriodUnit != nil || req.TimePeriodStartedAt != nil {
+			return errors.New(errors.CodeInvalidParam, "笔数轮询策略参数不完整")
+		}
+	case model.PaymentMerchantStrategyTime:
+		if req.TimePeriodValue == nil || *req.TimePeriodValue < 1 || req.TimePeriodUnit == nil || !validTimeUnit(*req.TimePeriodUnit) || req.TimePeriodStartedAt == nil || req.ThresholdAmount != nil || req.ThresholdCount != nil || req.StatisticCycle != nil {
+			return errors.New(errors.CodeInvalidParam, "时间轮询策略参数不完整")
+		}
+	default:
+		return errors.New(errors.CodeInvalidParam, "不支持的商户池轮询策略")
+	}
+	return nil
+}
+
+func validStatisticCycle(value string) bool {
+	return value == "round" || value == "day" || value == "month"
+}
+func validTimeUnit(value string) bool { return value == "minute" || value == "hour" || value == "day" }
+
+func (s *ManagementService) writeAudit(ctx context.Context, tx *gorm.DB, operation, description, key, name string, id uint, identity, before, after map[string]any) error {
+	if s.audit == nil {
+		return errors.New(errors.CodeInvalidStatus, "支付商户管理审计接缝未配置")
+	}
+	resourceID := strconv.FormatUint(uint64(id), 10)
+	return s.audit.WriteConfigChange(ctx, tx, systemconfigapp.ChangeAudit{
+		OperatorID: middleware.GetUserIDFromContext(ctx), OperationType: operation, Description: description,
+		ConfigKey: key, Module: "payment_merchant", ResourceID: &resourceID, DisplayName: name,
+		Identity: identity, BeforeData: before, AfterData: after, Result: constants.AuditResultSuccess,
+	})
+}
+
+func merchantAuditIdentity(m *model.PaymentMerchant) map[string]any {
+	return map[string]any{"id": m.ID, "name": m.Name, "payment_method": m.PaymentMethod, "provider_type": m.ProviderType, "merchant_identity": m.MerchantIdentity, "status": m.Status, "credential_version": m.CredentialVersion}
+}
+
+func poolAuditIdentity(p *model.PaymentMerchantPool) map[string]any {
+	return map[string]any{"id": p.ID, "name": p.Name, "payment_method": p.PaymentMethod, "strategy": p.Strategy, "status": p.Status, "routing_epoch": p.RoutingEpoch}
+}
+
+func authorizationAuditIdentity(a *model.WechatAuthorization) map[string]any {
+	return map[string]any{"id": a.ID, "status": a.Status, "credential_version": a.CredentialVersion, "oa_app_id": a.OaAppID, "miniapp_app_id": a.MiniappAppID}
+}
+
+// CreateMerchant 创建独立管理的支付商户。
+func (s *ManagementService) CreateMerchant(ctx context.Context, req dto.PaymentMerchantRequest) (*dto.PaymentMerchantResponse, error) {
+	if err := requireManager(ctx); err != nil {
+		return nil, err
+	}
+	if s == nil || s.db == nil || strings.TrimSpace(req.Name) == "" || len(req.Credentials) == 0 {
+		return nil, errors.New(errors.CodeInvalidParam, "商户参数或凭证不完整")
+	}
+	if !validPaymentMethod(strings.TrimSpace(req.PaymentMethod)) {
+		return nil, errors.New(errors.CodeInvalidParam, "支付方式仅支持微信或支付宝")
+	}
+	m := &model.PaymentMerchant{Name: strings.TrimSpace(req.Name), PaymentMethod: strings.TrimSpace(req.PaymentMethod), ProviderType: strings.TrimSpace(req.ProviderType), MerchantIdentity: strings.TrimSpace(req.MerchantIdentity), Credentials: req.Credentials, CredentialVersion: 1, Remark: strings.TrimSpace(req.Remark), BaseModel: model.BaseModel{Creator: middleware.GetUserIDFromContext(ctx), Updater: middleware.GetUserIDFromContext(ctx)}}
+	if req.Enabled {
+		m.Status = model.PaymentMerchantStatusEnabled
+	}
+	if m.MerchantIdentity == "" || m.ProviderType == "" {
+		return nil, errors.New(errors.CodeInvalidParam, "商户身份或服务商类型不能为空")
+	}
+	if err := validateMerchantConfiguration(m.PaymentMethod, m.ProviderType, m.MerchantIdentity, m.Credentials); err != nil {
+		return nil, err
+	}
+	if err := s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
+		if err := tx.Create(m).Error; err != nil {
+			return err
+		}
+		return s.writeAudit(ctx, tx, constants.AuditOperationPaymentConfigCreate, "创建支付商户", "payment_merchant:"+strconv.FormatUint(uint64(m.ID), 10), m.Name, m.ID, merchantAuditIdentity(m), nil, merchantAuditIdentity(m))
+	}); err != nil {
+		if appErr, ok := err.(*errors.AppError); ok {
+			return nil, appErr
+		}
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "创建支付商户失败")
+	}
+	return merchantResponse(m), nil
+}
+
+// ListMerchants returns the privileged configuration projection.
+
+// ListPools returns one page of merchant pools and their ordered members without per-pool member queries.
+func (s *ManagementService) ListPools(ctx context.Context, req dto.PaymentMerchantPoolListRequest) ([]*dto.PaymentMerchantPoolResponse, int64, error) {
+	if err := requireManager(ctx); err != nil {
+		return nil, 0, err
+	}
+	page, size := normalizePage(req.Page, req.PageSize)
+	query := s.db.WithContext(ctx).Model(&model.PaymentMerchantPool{})
+	var total int64
+	if err := query.Count(&total).Error; err != nil {
+		return nil, 0, errors.Wrap(errors.CodeDatabaseError, err, "统计商户池失败")
+	}
+	var pools []model.PaymentMerchantPool
+	if err := query.Order("id DESC").Offset((page - 1) * size).Limit(size).Find(&pools).Error; err != nil {
+		return nil, 0, errors.Wrap(errors.CodeDatabaseError, err, "查询商户池失败")
+	}
+	poolIDs := make([]uint, 0, len(pools))
+	for index := range pools {
+		poolIDs = append(poolIDs, pools[index].ID)
+	}
+	membersByPool := make(map[uint][]uint, len(pools))
+	if len(poolIDs) > 0 {
+		var members []model.PaymentMerchantPoolMember
+		if err := s.db.WithContext(ctx).Where("pool_id IN ?", poolIDs).Order("pool_id ASC, sort_order ASC").Find(&members).Error; err != nil {
+			return nil, 0, errors.Wrap(errors.CodeDatabaseError, err, "查询商户池成员失败")
+		}
+		for index := range members {
+			member := &members[index]
+			membersByPool[member.PoolID] = append(membersByPool[member.PoolID], member.MerchantID)
+		}
+	}
+	result := make([]*dto.PaymentMerchantPoolResponse, 0, len(pools))
+	for index := range pools {
+		pool := &pools[index]
+		result = append(result, &dto.PaymentMerchantPoolResponse{ID: pool.ID, Name: pool.Name, PaymentMethod: pool.PaymentMethod, Enabled: pool.Status == model.PaymentMerchantStatusEnabled, Strategy: pool.Strategy, ThresholdAmount: pool.ThresholdAmount, ThresholdCount: pool.ThresholdCount, StatisticCycle: pool.StatisticCycle, TimePeriodValue: pool.TimePeriodValue, TimePeriodUnit: pool.TimePeriodUnit, TimePeriodStartedAt: pool.TimePeriodStartedAt, RoutingEpoch: pool.RoutingEpoch, MemberIDs: membersByPool[pool.ID], Remark: pool.Remark})
+	}
+	return result, total, nil
+}
+
+// GetPool 查询一个商户池及其有序成员。
+func (s *ManagementService) GetPool(ctx context.Context, id uint) (*dto.PaymentMerchantPoolResponse, error) {
+	if err := requireManager(ctx); err != nil {
+		return nil, err
+	}
+	var pool model.PaymentMerchantPool
+	if err := s.db.WithContext(ctx).First(&pool, id).Error; err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return nil, errors.New(errors.CodeNotFound, "商户池不存在")
+		}
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询商户池失败")
+	}
+	return poolResponse(ctx, s.db, &pool)
+}
+
+// ListMerchants 分页查询特权商户配置。
+func (s *ManagementService) ListMerchants(ctx context.Context, req dto.PaymentMerchantListRequest) ([]*dto.PaymentMerchantResponse, int64, error) {
+	if err := requireManager(ctx); err != nil {
+		return nil, 0, err
+	}
+	page, size := normalizePage(req.Page, req.PageSize)
+	query := s.db.WithContext(ctx).Model(&model.PaymentMerchant{})
+	if req.PaymentMethod != nil {
+		query = query.Where("payment_method = ?", strings.TrimSpace(*req.PaymentMethod))
+	}
+	if req.Enabled != nil {
+		status := model.PaymentMerchantStatusDisabled
+		if *req.Enabled {
+			status = model.PaymentMerchantStatusEnabled
+		}
+		query = query.Where("status = ?", status)
+	}
+	var total int64
+	if err := query.Count(&total).Error; err != nil {
+		return nil, 0, errors.Wrap(errors.CodeDatabaseError, err, "查询支付商户失败")
+	}
+	var rows []model.PaymentMerchant
+	if err := query.Order("id DESC").Offset((page - 1) * size).Limit(size).Find(&rows).Error; err != nil {
+		return nil, 0, errors.Wrap(errors.CodeDatabaseError, err, "查询支付商户失败")
+	}
+	result := make([]*dto.PaymentMerchantResponse, 0, len(rows))
+	for index := range rows {
+		result = append(result, merchantResponse(&rows[index]))
+	}
+	return result, total, nil
+}
+
+// GetMerchant 查询一个特权商户配置。
+func (s *ManagementService) GetMerchant(ctx context.Context, id uint) (*dto.PaymentMerchantResponse, error) {
+	if err := requireManager(ctx); err != nil {
+		return nil, err
+	}
+	var m model.PaymentMerchant
+	if err := s.db.WithContext(ctx).First(&m, id).Error; err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return nil, errors.New(errors.CodeNotFound, "支付商户不存在")
+		}
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询支付商户失败")
+	}
+	return merchantResponse(&m), nil
+}
+
+// UpdateMerchant 更新商户凭证和可变配置。
+func (s *ManagementService) UpdateMerchant(ctx context.Context, id uint, req dto.PaymentMerchantUpdateRequest) (*dto.PaymentMerchantResponse, error) {
+	if err := requireManager(ctx); err != nil {
+		return nil, err
+	}
+	if req.PaymentMethod != nil && !validPaymentMethod(strings.TrimSpace(*req.PaymentMethod)) {
+		return nil, errors.New(errors.CodeInvalidParam, "支付方式仅支持微信或支付宝")
+	}
+	var m model.PaymentMerchant
+	if err := s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
+		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).First(&m, id).Error; err != nil {
+			return err
+		}
+		before := merchantAuditIdentity(&m)
+		previous := m
+		var refs int64
+		if err := tx.Model(&model.Payment{}).Where("merchant_id = ?", id).Count(&refs).Error; err != nil {
+			return err
+		}
+		if refs > 0 && ((req.PaymentMethod != nil && *req.PaymentMethod != m.PaymentMethod) || (req.ProviderType != nil && *req.ProviderType != m.ProviderType) || (req.MerchantIdentity != nil && *req.MerchantIdentity != m.MerchantIdentity)) {
+			return errors.New(errors.CodeConflict, "已被支付单引用，不能修改收款身份")
+		}
+		if req.Name != nil {
+			m.Name = strings.TrimSpace(*req.Name)
+		}
+		if req.PaymentMethod != nil {
+			m.PaymentMethod = strings.TrimSpace(*req.PaymentMethod)
+		}
+		if req.ProviderType != nil {
+			m.ProviderType = strings.TrimSpace(*req.ProviderType)
+		}
+		if req.MerchantIdentity != nil {
+			m.MerchantIdentity = strings.TrimSpace(*req.MerchantIdentity)
+		}
+		if req.Remark != nil {
+			m.Remark = strings.TrimSpace(*req.Remark)
+		}
+		if req.Enabled != nil {
+			m.Status = model.PaymentMerchantStatusDisabled
+			if *req.Enabled {
+				m.Status = model.PaymentMerchantStatusEnabled
+			}
+		}
+		if req.Credentials != nil && !reflect.DeepEqual(m.Credentials, *req.Credentials) {
+			m.Credentials = *req.Credentials
+		}
+		if previous.Name != m.Name || previous.PaymentMethod != m.PaymentMethod || previous.ProviderType != m.ProviderType || previous.MerchantIdentity != m.MerchantIdentity || previous.Status != m.Status || !reflect.DeepEqual(previous.Credentials, m.Credentials) {
+			m.CredentialVersion++
+		}
+		if err := validateMerchantConfiguration(m.PaymentMethod, m.ProviderType, m.MerchantIdentity, m.Credentials); err != nil {
+			return err
+		}
+		if err := tx.Save(&m).Error; err != nil {
+			return err
+		}
+		return s.writeAudit(ctx, tx, constants.AuditOperationPaymentConfigUpdate, "更新支付商户", "payment_merchant:"+strconv.FormatUint(uint64(m.ID), 10), m.Name, m.ID, merchantAuditIdentity(&m), before, merchantAuditIdentity(&m))
+	}); err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return nil, errors.New(errors.CodeNotFound, "支付商户不存在")
+		}
+		if appErr, ok := err.(*errors.AppError); ok {
+			return nil, appErr
+		}
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "更新支付商户失败")
+	}
+	return merchantResponse(&m), nil
+}
+
+// DeleteMerchant 仅在未被引用且二次确认后删除商户。
+func (s *ManagementService) DeleteMerchant(ctx context.Context, id uint, confirm bool) error {
+	if err := requireManager(ctx); err != nil {
+		return err
+	}
+	if !confirm {
+		return errors.New(errors.CodeInvalidParam, "删除商户必须二次确认")
+	}
+	return s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
+		var refs, members int64
+		var merchant model.PaymentMerchant
+		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).First(&merchant, id).Error; err != nil {
+			return err
+		}
+		before := merchantAuditIdentity(&merchant)
+		if err := tx.Model(&model.Payment{}).Where("merchant_id = ?", id).Count(&refs).Error; err != nil {
+			return err
+		}
+		if refs > 0 {
+			return errors.New(errors.CodeConflict, "已被支付单引用的商户不能删除")
+		}
+		if err := tx.Model(&model.PaymentMerchantPoolMember{}).Where("merchant_id = ?", id).Count(&members).Error; err != nil {
+			return err
+		}
+		if members > 0 {
+			return errors.New(errors.CodeConflict, "商户仍属于商户池")
+		}
+		r := tx.Delete(&model.PaymentMerchant{}, id)
+		if r.Error != nil {
+			return r.Error
+		}
+		if r.RowsAffected == 0 {
+			return errors.New(errors.CodeNotFound, "支付商户不存在")
+		}
+		if err := s.writeAudit(ctx, tx, constants.AuditOperationPaymentConfigDelete, "删除支付商户", "payment_merchant:"+strconv.FormatUint(uint64(merchant.ID), 10), merchant.Name, merchant.ID, before, before, nil); err != nil {
+			return err
+		}
+		return nil
+	})
+}
+
+// SavePool 创建或更新商户池，并原子替换有序成员。
+func (s *ManagementService) SavePool(ctx context.Context, id uint, req dto.PaymentMerchantPoolRequest) (*dto.PaymentMerchantPoolResponse, error) {
+	if err := requireManager(ctx); err != nil {
+		return nil, err
+	}
+	if err := validatePoolRequest(req); err != nil {
+		return nil, err
+	}
+	if len(req.MemberIDs) == 0 {
+		return nil, errors.New(errors.CodeInvalidParam, "商户池至少需要一个商户")
+	}
+	var pool model.PaymentMerchantPool
+	err := s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
+		creating := id == 0
+		var previousMemberIDs []uint
+		if !creating {
+			if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).First(&pool, id).Error; err != nil {
+				return err
+			}
+			var previousMembers []model.PaymentMerchantPoolMember
+			if err := tx.Where("pool_id = ?", pool.ID).Order("sort_order ASC").Find(&previousMembers).Error; err != nil {
+				return err
+			}
+			previousMemberIDs = make([]uint, 0, len(previousMembers))
+			for _, member := range previousMembers {
+				previousMemberIDs = append(previousMemberIDs, member.MerchantID)
+			}
+		} else {
+			pool.Creator = middleware.GetUserIDFromContext(ctx)
+			pool.RoutingEpoch = 1
+		}
+		before := poolAuditIdentity(&pool)
+		if err := validatePoolMembers(ctx, tx, req.PaymentMethod, req.MemberIDs); err != nil {
+			return err
+		}
+		if !creating && poolEpochChanged(&pool, &req, previousMemberIDs) {
+			pool.RoutingEpoch++
+		}
+		pool.Name, pool.PaymentMethod, pool.Strategy, pool.Remark = strings.TrimSpace(req.Name), strings.TrimSpace(req.PaymentMethod), strings.TrimSpace(req.Strategy), strings.TrimSpace(req.Remark)
+		pool.ThresholdAmount, pool.ThresholdCount, pool.StatisticCycle, pool.TimePeriodValue, pool.TimePeriodUnit, pool.TimePeriodStartedAt = req.ThresholdAmount, req.ThresholdCount, req.StatisticCycle, req.TimePeriodValue, req.TimePeriodUnit, req.TimePeriodStartedAt
+		if req.Enabled {
+			var others int64
+			if err := tx.Model(&model.PaymentMerchantPool{}).Where("payment_method = ? AND status = ? AND id <> ?", pool.PaymentMethod, model.PaymentMerchantStatusEnabled, pool.ID).Count(&others).Error; err != nil {
+				return err
+			}
+			if others > 0 {
+				return errors.New(errors.CodeConflict, "该支付方式已有启用商户池")
+			}
+		}
+		pool.Status = model.PaymentMerchantStatusDisabled
+		if req.Enabled {
+			pool.Status = model.PaymentMerchantStatusEnabled
+		}
+		pool.Updater = middleware.GetUserIDFromContext(ctx)
+		if creating {
+			if err := tx.Create(&pool).Error; err != nil {
+				return err
+			}
+		} else if err := tx.Save(&pool).Error; err != nil {
+			return err
+		}
+		if err := tx.Where("pool_id = ?", pool.ID).Delete(&model.PaymentMerchantPoolMember{}).Error; err != nil {
+			return err
+		}
+		members := make([]model.PaymentMerchantPoolMember, 0, len(req.MemberIDs))
+		for i, merchantID := range req.MemberIDs {
+			members = append(members, model.PaymentMerchantPoolMember{PoolID: pool.ID, MerchantID: merchantID, SortOrder: int64(i), BaseModel: model.BaseModel{Creator: middleware.GetUserIDFromContext(ctx), Updater: middleware.GetUserIDFromContext(ctx)}})
+		}
+		if err := tx.Create(&members).Error; err != nil {
+			return err
+		}
+		op := constants.AuditOperationPaymentConfigUpdate
+		summary := "更新商户池"
+		if creating {
+			op = constants.AuditOperationPaymentConfigCreate
+			summary = "创建商户池"
+		}
+		return s.writeAudit(ctx, tx, op, summary, "payment_merchant_pool:"+strconv.FormatUint(uint64(pool.ID), 10), pool.Name, pool.ID, poolAuditIdentity(&pool), before, poolAuditIdentity(&pool))
+	})
+	if err != nil {
+		if appErr, ok := err.(*errors.AppError); ok {
+			return nil, appErr
+		}
+		if err == gorm.ErrRecordNotFound {
+			return nil, errors.New(errors.CodeNotFound, "商户池不存在")
+		}
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "保存商户池失败")
+	}
+	return poolResponse(ctx, s.db, &pool)
+}
+
+// SetPoolEnabled enables or disables a pool after rechecking the active-pool and member invariants.
+func (s *ManagementService) SetPoolEnabled(ctx context.Context, id uint, enabled bool) (*dto.PaymentMerchantPoolResponse, error) {
+	if err := requireManager(ctx); err != nil {
+		return nil, err
+	}
+	var pool model.PaymentMerchantPool
+	err := s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
+		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).First(&pool, id).Error; err != nil {
+			return err
+		}
+		before := poolAuditIdentity(&pool)
+		if enabled {
+			var others int64
+			if err := tx.Model(&model.PaymentMerchantPool{}).Where("payment_method = ? AND status = ? AND id <> ?", pool.PaymentMethod, model.PaymentMerchantStatusEnabled, pool.ID).Count(&others).Error; err != nil {
+				return err
+			}
+			if others > 0 {
+				return errors.New(errors.CodeConflict, "该支付方式已有启用商户池")
+			}
+			var members []model.PaymentMerchantPoolMember
+			if err := tx.Where("pool_id = ?", pool.ID).Order("sort_order ASC").Find(&members).Error; err != nil {
+				return err
+			}
+			ids := make([]uint, 0, len(members))
+			for _, member := range members {
+				ids = append(ids, member.MerchantID)
+			}
+			if err := validatePoolMembers(ctx, tx, pool.PaymentMethod, ids); err != nil {
+				return err
+			}
+			pool.Status = model.PaymentMerchantStatusEnabled
+		} else {
+			pool.Status = model.PaymentMerchantStatusDisabled
+		}
+		pool.Updater = middleware.GetUserIDFromContext(ctx)
+		if err := tx.Save(&pool).Error; err != nil {
+			return err
+		}
+		op := constants.AuditOperationPaymentConfigDeactivate
+		summary := "停用商户池"
+		if enabled {
+			op = constants.AuditOperationPaymentConfigActivate
+			summary = "启用商户池"
+		}
+		return s.writeAudit(ctx, tx, op, summary, "payment_merchant_pool:"+strconv.FormatUint(uint64(pool.ID), 10), pool.Name, pool.ID, poolAuditIdentity(&pool), before, poolAuditIdentity(&pool))
+	})
+	if err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return nil, errors.New(errors.CodeNotFound, "商户池不存在")
+		}
+		if appErr, ok := err.(*errors.AppError); ok {
+			return nil, appErr
+		}
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "更新商户池状态失败")
+	}
+	return poolResponse(ctx, s.db, &pool)
+}
+
+func validatePoolMembers(ctx context.Context, tx *gorm.DB, method string, ids []uint) error {
+	seen := map[uint]struct{}{}
+
+	for _, id := range ids {
+		if id == 0 {
+			return errors.New(errors.CodeInvalidParam, "商户ID无效")
+		}
+		if _, ok := seen[id]; ok {
+			return errors.New(errors.CodeInvalidParam, "商户池成员不能重复")
+		}
+		seen[id] = struct{}{}
+	}
+	var merchants []model.PaymentMerchant
+	if err := tx.WithContext(ctx).Where("id IN ? AND payment_method = ? AND status = ?", ids, method, model.PaymentMerchantStatusEnabled).Find(&merchants).Error; err != nil {
+		return err
+	}
+	if len(merchants) != len(ids) {
+		return errors.New(errors.CodeConflict, "商户池成员必须存在、启用且支付方式一致")
+	}
+	for index := range merchants {
+		merchant := &merchants[index]
+		if err := validateMerchantConfiguration(merchant.PaymentMethod, merchant.ProviderType, merchant.MerchantIdentity, merchant.Credentials); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+func poolEpochChanged(pool *model.PaymentMerchantPool, request *dto.PaymentMerchantPoolRequest, previousMemberIDs []uint) bool {
+	if pool.PaymentMethod != strings.TrimSpace(request.PaymentMethod) ||
+		pool.Strategy != request.Strategy ||
+		!sameString(pool.StatisticCycle, request.StatisticCycle) ||
+		!sameInt64(pool.TimePeriodValue, request.TimePeriodValue) ||
+		!sameString(pool.TimePeriodUnit, request.TimePeriodUnit) ||
+		!sameTime(pool.TimePeriodStartedAt, request.TimePeriodStartedAt) {
+		return true
+	}
+	if sameMemberOrder(previousMemberIDs, request.MemberIDs) {
+		return false
+	}
+	return pool.StatisticCycle == nil || (*pool.StatisticCycle != "day" && *pool.StatisticCycle != "month") || !sameMemberSet(previousMemberIDs, request.MemberIDs)
+}
+
+func sameMemberOrder(left, right []uint) bool {
+	if len(left) != len(right) {
+		return false
+	}
+	for i := range left {
+		if left[i] != right[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func sameMemberSet(left, right []uint) bool {
+	if len(left) != len(right) {
+		return false
+	}
+	seen := make(map[uint]struct{}, len(left))
+	for _, id := range left {
+		seen[id] = struct{}{}
+	}
+	for _, id := range right {
+		if _, ok := seen[id]; !ok {
+			return false
+		}
+	}
+	return true
+}
+
+func sameString(left, right *string) bool {
+	if left == nil || right == nil {
+		return left == right
+	}
+	return *left == *right
+}
+
+func sameInt64(left, right *int64) bool {
+	if left == nil || right == nil {
+		return left == right
+	}
+	return *left == *right
+}
+
+func sameTime(a, b *time.Time) bool {
+	if a == nil || b == nil {
+		return a == b
+	}
+	return a.Equal(*b)
+}
+func merchantResponse(m *model.PaymentMerchant) *dto.PaymentMerchantResponse {
+	return &dto.PaymentMerchantResponse{ID: m.ID, Name: m.Name, PaymentMethod: m.PaymentMethod, ProviderType: m.ProviderType, MerchantIdentity: m.MerchantIdentity, Credentials: m.Credentials, CredentialVersion: m.CredentialVersion, Enabled: m.Status == model.PaymentMerchantStatusEnabled, Remark: m.Remark, CreatedAt: m.CreatedAt, UpdatedAt: m.UpdatedAt}
+}
+func poolResponse(ctx context.Context, db *gorm.DB, p *model.PaymentMerchantPool) (*dto.PaymentMerchantPoolResponse, error) {
+	var rows []model.PaymentMerchantPoolMember
+	if err := db.WithContext(ctx).Where("pool_id = ?", p.ID).Order("sort_order ASC").Find(&rows).Error; err != nil {
+		return nil, err
+	}
+	ids := make([]uint, 0, len(rows))
+	for _, row := range rows {
+		ids = append(ids, row.MerchantID)
+	}
+	return &dto.PaymentMerchantPoolResponse{ID: p.ID, Name: p.Name, PaymentMethod: p.PaymentMethod, Enabled: p.Status == model.PaymentMerchantStatusEnabled, Strategy: p.Strategy, ThresholdAmount: p.ThresholdAmount, ThresholdCount: p.ThresholdCount, StatisticCycle: p.StatisticCycle, TimePeriodValue: p.TimePeriodValue, TimePeriodUnit: p.TimePeriodUnit, TimePeriodStartedAt: p.TimePeriodStartedAt, RoutingEpoch: p.RoutingEpoch, MemberIDs: ids, Remark: p.Remark}, nil
+}
+
+// GetAuthorization 查询特权全局授权配置。
+func (s *ManagementService) GetAuthorization(ctx context.Context) (*dto.WechatAuthorizationResponse, error) {
+	if err := requireManager(ctx); err != nil {
+		return nil, err
+	}
+	var a model.WechatAuthorization
+	if err := s.db.WithContext(ctx).First(&a).Error; err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return nil, nil
+		}
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询微信授权配置失败")
+	}
+	return authorizationResponse(&a), nil
+}
+
+// SaveAuthorization 创建或更新唯一启用的授权配置。
+func (s *ManagementService) SaveAuthorization(ctx context.Context, req dto.WechatAuthorizationRequest) (*dto.WechatAuthorizationResponse, error) {
+	if err := requireManager(ctx); err != nil {
+		return nil, err
+	}
+	if req.Enabled && (strings.TrimSpace(req.OaAppID) == "" || strings.TrimSpace(req.OaAppSecret) == "" || strings.TrimSpace(req.MiniappAppID) == "" || strings.TrimSpace(req.MiniappAppSecret) == "") {
+		return nil, errors.New(errors.CodeInvalidParam, "启用微信授权配置时公众号和小程序凭证必须完整")
+	}
+	var authorization model.WechatAuthorization
+	err := s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
+		err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).First(&authorization).Error
+		if err != nil && err != gorm.ErrRecordNotFound {
+			return err
+		}
+		previousStatus := authorization.Status
+		creating := err == gorm.ErrRecordNotFound
+		before := authorizationAuditIdentity(&authorization)
+		if creating {
+			authorization.Creator = middleware.GetUserIDFromContext(ctx)
+			authorization.CredentialVersion = 1
+		}
+		changed := authorization.OaAppID != req.OaAppID || authorization.OaAppSecret != req.OaAppSecret || authorization.OaToken != req.OaToken || authorization.OaAesKey != req.OaAesKey || authorization.OaOAuthRedirectURL != req.OaOAuthRedirectURL || authorization.MiniappAppID != req.MiniappAppID || authorization.MiniappAppSecret != req.MiniappAppSecret
+		authorization.OaAppID, authorization.OaAppSecret, authorization.OaToken, authorization.OaAesKey, authorization.OaOAuthRedirectURL, authorization.MiniappAppID, authorization.MiniappAppSecret = req.OaAppID, req.OaAppSecret, req.OaToken, req.OaAesKey, req.OaOAuthRedirectURL, req.MiniappAppID, req.MiniappAppSecret
+		authorization.Status = model.PaymentMerchantStatusDisabled
+		if req.Enabled {
+			authorization.Status = model.PaymentMerchantStatusEnabled
+		}
+		if !creating && (changed || previousStatus != authorization.Status) {
+			authorization.CredentialVersion++
+		}
+		authorization.Updater = middleware.GetUserIDFromContext(ctx)
+		if creating {
+			if err := tx.Create(&authorization).Error; err != nil {
+				return err
+			}
+		} else {
+			if err := tx.Save(&authorization).Error; err != nil {
+				return err
+			}
+		}
+		op := constants.AuditOperationPaymentConfigUpdate
+		summary := "更新微信授权配置"
+		if creating {
+			op = constants.AuditOperationPaymentConfigCreate
+			summary = "创建微信授权配置"
+		}
+		return s.writeAudit(ctx, tx, op, summary, "wechat_authorization:"+strconv.FormatUint(uint64(authorization.ID), 10), "微信授权配置", authorization.ID, authorizationAuditIdentity(&authorization), before, authorizationAuditIdentity(&authorization))
+	})
+	if err != nil {
+		if appErr, ok := err.(*errors.AppError); ok {
+			return nil, appErr
+		}
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "保存微信授权配置失败")
+	}
+	return authorizationResponse(&authorization), nil
+}
+func authorizationResponse(a *model.WechatAuthorization) *dto.WechatAuthorizationResponse {
+	return &dto.WechatAuthorizationResponse{ID: a.ID, OaAppID: a.OaAppID, OaAppSecret: a.OaAppSecret, OaToken: a.OaToken, OaAesKey: a.OaAesKey, OaOAuthRedirectURL: a.OaOAuthRedirectURL, MiniappAppID: a.MiniappAppID, MiniappAppSecret: a.MiniappAppSecret, CredentialVersion: a.CredentialVersion, Enabled: a.Status == model.PaymentMerchantStatusEnabled, UpdatedAt: a.UpdatedAt}
+}

internal/application/merchantpayment/routing.go

@@ -0,0 +1,386 @@
+package merchantpayment
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/bytedance/sonic"
+	"github.com/redis/go-redis/v9"
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+
+	"github.com/break/junhong_cmp_fiber/internal/model"
+	"github.com/break/junhong_cmp_fiber/pkg/errors"
+)
+
+// RouteSelection is the non-sensitive route frozen onto a new payment.
+type RouteSelection struct {
+	Merchant *model.PaymentMerchant
+	Pool     *model.PaymentMerchantPool
+}
+
+// RuntimeLoader loads current merchant and authorization credentials by version.
+type RuntimeLoader struct {
+	db    *gorm.DB
+	redis *redis.Client
+}
+
+// merchantCachePayload is used only for the internal versioned Redis cache and deliberately includes credentials.
+// It must never be used for DTOs, logs, audits, or payment snapshots.
+type merchantCachePayload struct {
+	ID                uint        `json:"id"`
+	Name              string      `json:"name"`
+	PaymentMethod     string      `json:"payment_method"`
+	ProviderType      string      `json:"provider_type"`
+	MerchantIdentity  string      `json:"merchant_identity"`
+	Credentials       model.JSONB `json:"credentials"`
+	CredentialVersion int64       `json:"credential_version"`
+	Status            int         `json:"status"`
+	Remark            string      `json:"remark"`
+}
+
+func merchantCachePayloadFrom(merchant *model.PaymentMerchant) merchantCachePayload {
+	return merchantCachePayload{ID: merchant.ID, Name: merchant.Name, PaymentMethod: merchant.PaymentMethod, ProviderType: merchant.ProviderType, MerchantIdentity: merchant.MerchantIdentity, Credentials: merchant.Credentials, CredentialVersion: merchant.CredentialVersion, Status: merchant.Status, Remark: merchant.Remark}
+}
+
+func (p merchantCachePayload) merchant() *model.PaymentMerchant {
+	return &model.PaymentMerchant{Model: gorm.Model{ID: p.ID}, Name: p.Name, PaymentMethod: p.PaymentMethod, ProviderType: p.ProviderType, MerchantIdentity: p.MerchantIdentity, Credentials: p.Credentials, CredentialVersion: p.CredentialVersion, Status: p.Status, Remark: p.Remark}
+}
+
+// authorizationCachePayload is used only for the internal versioned Redis cache and deliberately includes secrets.
+// It must never be used for DTOs, logs, audits, or payment snapshots.
+type authorizationCachePayload struct {
+	ID                 uint   `json:"id"`
+	OaAppID            string `json:"oa_app_id"`
+	OaAppSecret        string `json:"oa_app_secret"`
+	OaToken            string `json:"oa_token"`
+	OaAesKey           string `json:"oa_aes_key"`
+	OaOAuthRedirectURL string `json:"oa_oauth_redirect_url"`
+	MiniappAppID       string `json:"miniapp_app_id"`
+	MiniappAppSecret   string `json:"miniapp_app_secret"`
+	CredentialVersion  int64  `json:"credential_version"`
+	Status             int    `json:"status"`
+}
+
+func authorizationCachePayloadFrom(authorization *model.WechatAuthorization) authorizationCachePayload {
+	return authorizationCachePayload{ID: authorization.ID, OaAppID: authorization.OaAppID, OaAppSecret: authorization.OaAppSecret, OaToken: authorization.OaToken, OaAesKey: authorization.OaAesKey, OaOAuthRedirectURL: authorization.OaOAuthRedirectURL, MiniappAppID: authorization.MiniappAppID, MiniappAppSecret: authorization.MiniappAppSecret, CredentialVersion: authorization.CredentialVersion, Status: authorization.Status}
+}
+
+func (p authorizationCachePayload) authorization() *model.WechatAuthorization {
+	return &model.WechatAuthorization{Model: gorm.Model{ID: p.ID}, OaAppID: p.OaAppID, OaAppSecret: p.OaAppSecret, OaToken: p.OaToken, OaAesKey: p.OaAesKey, OaOAuthRedirectURL: p.OaOAuthRedirectURL, MiniappAppID: p.MiniappAppID, MiniappAppSecret: p.MiniappAppSecret, CredentialVersion: p.CredentialVersion, Status: p.Status}
+}
+
+func NewRuntimeLoader(db *gorm.DB, redis *redis.Client) *RuntimeLoader {
+	return &RuntimeLoader{db: db, redis: redis}
+}
+
+// LoadMerchant first reads the current version from the primary database, then uses only that version's cache entry.
+// Disabled merchants remain loadable for frozen historical payments.
+func (l *RuntimeLoader) LoadMerchant(ctx context.Context, id uint) (*model.PaymentMerchant, error) {
+	if l == nil || l.db == nil {
+		return nil, errors.New(errors.CodeServiceUnavailable, "支付商户加载能力未配置")
+	}
+	return l.loadMerchant(ctx, l.db, id)
+}
+
+// loadMerchant 先从当前事务或主库读取版本，再仅命中该版本的缓存。
+// 版本在凭证事务提交时递增，因此提交前遗留的旧缓存永远不会被新读取命中。
+func (l *RuntimeLoader) loadMerchant(ctx context.Context, db *gorm.DB, id uint) (*model.PaymentMerchant, error) {
+	var current model.PaymentMerchant
+	if err := db.WithContext(ctx).First(&current, id).Error; err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return nil, errors.New(errors.CodeNotFound, "支付商户不存在")
+		}
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "读取支付商户失败")
+	}
+	key := fmt.Sprintf("payment:merchant:%d:%d", current.ID, current.CredentialVersion)
+	if l.redis != nil {
+		if text, err := l.redis.Get(ctx, key).Result(); err == nil {
+			var cached merchantCachePayload
+			if sonic.UnmarshalString(text, &cached) == nil && cached.ID == current.ID && cached.CredentialVersion == current.CredentialVersion {
+				return cached.merchant(), nil
+			}
+		}
+	}
+	if l.redis != nil {
+		if text, err := sonic.MarshalString(merchantCachePayloadFrom(&current)); err == nil {
+			_ = l.redis.Set(ctx, key, text, time.Hour).Err()
+		}
+	}
+	return &current, nil
+}
+
+// LoadAuthorization first reads the current enabled version and only then resolves its versioned cache entry.
+func (l *RuntimeLoader) LoadAuthorization(ctx context.Context) (*model.WechatAuthorization, error) {
+	if l == nil || l.db == nil {
+		return nil, errors.New(errors.CodeServiceUnavailable, "微信授权加载能力未配置")
+	}
+	var current model.WechatAuthorization
+	if err := l.db.WithContext(ctx).Where("status = ?", model.PaymentMerchantStatusEnabled).First(&current).Error; err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return nil, errors.New(errors.CodeWechatConfigUnavailable, "微信授权未配置")
+		}
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "读取微信授权配置失败")
+	}
+	key := fmt.Sprintf("payment:wechat-authorization:%d:%d", current.ID, current.CredentialVersion)
+	if l.redis != nil {
+		if text, err := l.redis.Get(ctx, key).Result(); err == nil {
+			var cached authorizationCachePayload
+			if sonic.UnmarshalString(text, &cached) == nil && cached.ID == current.ID && cached.CredentialVersion == current.CredentialVersion {
+				return cached.authorization(), nil
+			}
+		}
+	}
+	if l.redis != nil {
+		if text, err := sonic.MarshalString(authorizationCachePayloadFrom(&current)); err == nil {
+			_ = l.redis.Set(ctx, key, text, time.Hour).Err()
+		}
+	}
+	return &current, nil
+}
+
+// MerchantConfig adapts the merchant credential payload to existing channel constructors without persisting credentials in a payment snapshot.
+func MerchantConfig(merchant *model.PaymentMerchant, authorization *model.WechatAuthorization) (*model.WechatConfig, error) {
+	if merchant == nil {
+		return nil, errors.New(errors.CodeNoPaymentConfig, "支付商户不存在")
+	}
+	if authorization == nil {
+		authorization = &model.WechatAuthorization{}
+	}
+	raw, err := sonic.Marshal(merchant.Credentials)
+	if err != nil {
+		return nil, errors.Wrap(errors.CodeInvalidParam, err, "支付商户凭证格式无效")
+	}
+	var cfg model.WechatConfig
+	if err := sonic.Unmarshal(raw, &cfg); err != nil {
+		return nil, errors.Wrap(errors.CodeInvalidParam, err, "支付商户凭证格式无效")
+	}
+	cfg.ID = merchant.ID
+	cfg.ProviderType = merchant.ProviderType
+	cfg.IsActive = true
+	if authorization != nil {
+		cfg.OaAppID = authorization.OaAppID
+		cfg.OaAppSecret = authorization.OaAppSecret
+		cfg.OaToken = authorization.OaToken
+		cfg.OaAesKey = authorization.OaAesKey
+		cfg.OaOAuthRedirectURL = authorization.OaOAuthRedirectURL
+		cfg.MiniappAppID = authorization.MiniappAppID
+		cfg.MiniappAppSecret = authorization.MiniappAppSecret
+	}
+	return &cfg, nil
+}
+
+// MerchantConfigWithAuthorization 在需要 AppID 的渠道实例前，按当前版本加载全局微信授权配置。
+// 授权字段只进入内存中的渠道配置，绝不写入支付快照、普通 DTO、日志、审计或导出。
+func (l *RuntimeLoader) MerchantConfigWithAuthorization(ctx context.Context, merchant *model.PaymentMerchant) (*model.WechatConfig, error) {
+	authorization, err := l.LoadAuthorization(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return MerchantConfig(merchant, authorization)
+}
+
+// SelectForNewPayment atomically reads the active pool and chooses its current eligible member.
+func (l *RuntimeLoader) SelectForNewPayment(ctx context.Context, paymentMethod string, now time.Time) (*RouteSelection, error) {
+	if l == nil || l.db == nil {
+		return nil, errors.New(errors.CodeServiceUnavailable, "商户池路由能力未配置")
+	}
+	var out *RouteSelection
+	err := l.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
+		var err error
+		out, err = l.SelectForNewPaymentWithTx(ctx, tx, paymentMethod, now)
+		return err
+	})
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// SelectForNewPaymentWithTx chooses an eligible merchant while retaining the caller's business transaction.
+func (l *RuntimeLoader) SelectForNewPaymentWithTx(ctx context.Context, tx *gorm.DB, paymentMethod string, now time.Time) (*RouteSelection, error) {
+	if l == nil || tx == nil {
+		return nil, errors.New(errors.CodeServiceUnavailable, "商户池路由能力未配置")
+	}
+	var pool model.PaymentMerchantPool
+	if err := tx.WithContext(ctx).Clauses(clause.Locking{Strength: "UPDATE"}).Where("payment_method = ? AND status = ?", paymentMethod, model.PaymentMerchantStatusEnabled).First(&pool).Error; err != nil {
+		if err == gorm.ErrRecordNotFound {
+			return nil, errors.New(errors.CodeNoPaymentConfig, "暂无可用商户")
+		}
+		return nil, err
+	}
+	var members []model.PaymentMerchantPoolMember
+	if err := tx.WithContext(ctx).Where("pool_id = ?", pool.ID).Order("sort_order ASC").Find(&members).Error; err != nil {
+		return nil, err
+	}
+	if len(members) == 0 {
+		return nil, errors.New(errors.CodeNoPaymentConfig, "暂无可用商户")
+	}
+	ids := make([]uint, 0, len(members))
+	for _, member := range members {
+		ids = append(ids, member.MerchantID)
+	}
+	var merchants []model.PaymentMerchant
+	if err := tx.WithContext(ctx).Clauses(clause.Locking{Strength: "UPDATE"}).Where("id IN ? AND payment_method = ? AND status = ?", ids, pool.PaymentMethod, model.PaymentMerchantStatusEnabled).Find(&merchants).Error; err != nil {
+		return nil, err
+	}
+	byID := make(map[uint]*model.PaymentMerchant, len(merchants))
+	for i := range merchants {
+		byID[merchants[i].ID] = &merchants[i]
+	}
+	ordered := make([]*model.PaymentMerchant, 0, len(members))
+	for _, member := range members {
+		if merchant := byID[member.MerchantID]; merchant != nil {
+			ordered = append(ordered, merchant)
+		}
+	}
+	chosen, err := chooseMerchant(ctx, tx, &pool, ordered, now)
+	if err != nil {
+		return nil, err
+	}
+	// 新支付在冻结前也按“商户 ID + 当前版本”读取缓存；事务锁保证本次
+	// 选择与凭证版本属于同一提交边界，避免新建支付误用旧版本缓存。
+	chosen, err = l.loadMerchant(ctx, tx, chosen.ID)
+	if err != nil {
+		return nil, err
+	}
+	return &RouteSelection{Merchant: chosen, Pool: &pool}, nil
+}
+
+func chooseMerchant(ctx context.Context, tx *gorm.DB, pool *model.PaymentMerchantPool, merchants []*model.PaymentMerchant, now time.Time) (*model.PaymentMerchant, error) {
+	if len(merchants) == 0 {
+		return nil, errors.New(errors.CodeNoPaymentConfig, "暂无可用商户")
+	}
+	if pool.Strategy == model.PaymentMerchantStrategyTime {
+		return chooseTimedMerchant(pool, merchants, now)
+	}
+	if pool.Strategy != model.PaymentMerchantStrategyAmount && pool.Strategy != model.PaymentMerchantStrategyCount {
+		return nil, errors.New(errors.CodeInvalidStatus, "商户池轮询策略无效")
+	}
+	if pool.StatisticCycle == nil {
+		return nil, errors.New(errors.CodeInvalidStatus, "商户池统计周期未配置")
+	}
+
+	query := tx.WithContext(ctx).Where("pool_id = ? AND routing_epoch = ?", pool.ID, pool.RoutingEpoch)
+	if start, limited := routingWindowStart(*pool.StatisticCycle, now); limited {
+		query = query.Where("paid_at >= ?", start)
+	}
+	var rows []model.PaymentMerchantRoutingSuccess
+	if err := query.Find(&rows).Error; err != nil {
+		return nil, err
+	}
+	amounts := make(map[uint]int64, len(merchants))
+	counts := make(map[uint]int64, len(merchants))
+	for _, row := range rows {
+		amounts[row.MerchantID] += row.Amount
+		counts[row.MerchantID]++
+	}
+	for _, merchant := range merchants {
+		if pool.Strategy == model.PaymentMerchantStrategyAmount {
+			if pool.ThresholdAmount == nil {
+				return nil, errors.New(errors.CodeInvalidStatus, "金额轮询阈值未配置")
+			}
+			if amounts[merchant.ID] < *pool.ThresholdAmount {
+				return merchant, nil
+			}
+			continue
+		}
+		if pool.ThresholdCount == nil {
+			return nil, errors.New(errors.CodeInvalidStatus, "笔数轮询阈值未配置")
+		}
+		if counts[merchant.ID] < *pool.ThresholdCount {
+			return merchant, nil
+		}
+	}
+	if *pool.StatisticCycle != "round" {
+		return nil, errors.New(errors.CodeNoPaymentConfig, "当前统计周期内暂无可用商户")
+	}
+	if err := advanceRoutingEpoch(ctx, tx, pool); err != nil {
+		return nil, err
+	}
+	return merchants[0], nil
+}
+
+func chooseTimedMerchant(pool *model.PaymentMerchantPool, merchants []*model.PaymentMerchant, now time.Time) (*model.PaymentMerchant, error) {
+	if pool.TimePeriodStartedAt == nil || pool.TimePeriodValue == nil || pool.TimePeriodUnit == nil {
+		return nil, errors.New(errors.CodeInvalidStatus, "时间轮询配置不完整")
+	}
+	unit := time.Minute
+	switch *pool.TimePeriodUnit {
+	case "hour":
+		unit = time.Hour
+	case "day":
+		unit = 24 * time.Hour
+	case "minute":
+	default:
+		return nil, errors.New(errors.CodeInvalidStatus, "时间轮询单位无效")
+	}
+	period := unit * time.Duration(*pool.TimePeriodValue)
+	if period <= 0 {
+		return nil, errors.New(errors.CodeInvalidStatus, "时间轮询周期无效")
+	}
+	slot := now.Sub(*pool.TimePeriodStartedAt) / period
+	if slot < 0 {
+		slot = 0
+	}
+	return merchants[int(slot%time.Duration(len(merchants)))], nil
+}
+
+func routingWindowStart(cycle string, now time.Time) (time.Time, bool) {
+	local := now.In(now.Location())
+	switch cycle {
+	case "day":
+		return time.Date(local.Year(), local.Month(), local.Day(), 0, 0, 0, 0, local.Location()), true
+	case "month":
+		return time.Date(local.Year(), local.Month(), 1, 0, 0, 0, 0, local.Location()), true
+	default:
+		return time.Time{}, false
+	}
+}
+
+func advanceRoutingEpoch(ctx context.Context, tx *gorm.DB, pool *model.PaymentMerchantPool) error {
+	next := pool.RoutingEpoch + 1
+	result := tx.WithContext(ctx).Model(&model.PaymentMerchantPool{}).Where("id = ? AND routing_epoch = ?", pool.ID, pool.RoutingEpoch).Update("routing_epoch", next)
+	if result.Error != nil {
+		return result.Error
+	}
+	if result.RowsAffected != 1 {
+		return errors.New(errors.CodeConflict, "商户池统计世代已变化")
+	}
+	pool.RoutingEpoch = next
+	return nil
+}
+
+// FreezeRoute writes only non-sensitive route facts onto the payment.
+func FreezeRoute(payment *model.Payment, route *RouteSelection) {
+	if payment == nil || route == nil || route.Merchant == nil || route.Pool == nil {
+		return
+	}
+	payment.MerchantID = &route.Merchant.ID
+	payment.MerchantPoolID = &route.Pool.ID
+	payment.MerchantIdentity = route.Merchant.MerchantIdentity
+	payment.MerchantNameSnapshot = route.Merchant.Name
+	payment.MerchantPaymentMethodSnapshot = route.Merchant.PaymentMethod
+	payment.MerchantProviderTypeSnapshot = route.Merchant.ProviderType
+	payment.MerchantPoolNameSnapshot = route.Pool.Name
+	payment.RoutingStrategySnapshot = route.Pool.Strategy
+	epoch := route.Pool.RoutingEpoch
+	payment.RoutingEpoch = &epoch
+}
+
+// RecordFirstSuccess 在支付成功事务内写入支付不可变的路由事实。
+func RecordFirstSuccess(ctx context.Context, tx *gorm.DB, payment *model.Payment, paidAt time.Time) error {
+	if payment == nil || payment.MerchantID == nil || payment.MerchantPoolID == nil || payment.RoutingEpoch == nil {
+		return nil
+	}
+	fact := model.PaymentMerchantRoutingSuccess{PaymentID: payment.ID, MerchantID: *payment.MerchantID, PoolID: *payment.MerchantPoolID, RoutingEpoch: *payment.RoutingEpoch, Amount: payment.Amount, PaidAt: paidAt}
+	if err := tx.WithContext(ctx).Create(&fact).Error; err != nil {
+		if strings.Contains(err.Error(), "duplicate key") {
+			return nil
+		}
+		return errors.Wrap(errors.CodeDatabaseError, err, "写入商户池成功统计失败")
+	}
+	return nil
+}