diff --git a/src/modules/auth/apiKeys.controller.ts b/src/modules/auth/apiKeys.controller.ts
index bb6cb71..a637387 100644
--- a/src/modules/auth/apiKeys.controller.ts
+++ b/src/modules/auth/apiKeys.controller.ts
@@ -181,7 +181,10 @@ class ApiKeysController {
       }
 
       const dto: UpdateApiKeyDto = {
-        ...validation.data,
+        name: validation.data.name,
+        scope: validation.data.scope ?? undefined,
+        allowed_ips: validation.data.allowed_ips ?? undefined,
+        is_active: validation.data.is_active,
         expiration_date: validation.data.expiration_date
           ? new Date(validation.data.expiration_date)
           : validation.data.expiration_date === null
diff --git a/src/modules/billing-usage/services/invoices.service.ts b/src/modules/billing-usage/services/invoices.service.ts
index 117fc8e..ac56c9d 100644
--- a/src/modules/billing-usage/services/invoices.service.ts
+++ b/src/modules/billing-usage/services/invoices.service.ts
@@ -76,15 +76,14 @@ export class InvoicesService {
       const discount = itemTotal * ((itemDto.discountPercent || 0) / 100);
 
       const item = this.itemRepository.create({
-        invoiceId: savedInvoice.id,
         itemType: itemDto.itemType,
         description: itemDto.description,
         quantity: itemDto.quantity,
         unitPrice: itemDto.unitPrice,
-        discountPercent: itemDto.discountPercent || 0,
         subtotal: itemTotal - discount,
         metadata: itemDto.metadata || {},
       });
+      item.invoiceId = savedInvoice.id;
 
       await this.itemRepository.save(item);
     }
@@ -310,7 +309,7 @@ export class InvoicesService {
 
     invoice.paidAmount = newPaidAmount;
     invoice.paymentMethod = dto.paymentMethod;
-    invoice.paymentReference = dto.paymentReference;
+    invoice.paymentReference = dto.paymentReference || '';
 
     if (newPaidAmount >= total) {
       invoice.status = 'paid';
diff --git a/src/modules/billing-usage/services/subscriptions.service.ts b/src/modules/billing-usage/services/subscriptions.service.ts
index c693f05..25851b1 100644
--- a/src/modules/billing-usage/services/subscriptions.service.ts
+++ b/src/modules/billing-usage/services/subscriptions.service.ts
@@ -135,7 +135,7 @@ export class SubscriptionsService {
       throw new Error('Subscription is already cancelled');
     }
 
-    subscription.cancellationReason = dto.reason;
+    subscription.cancellationReason = dto.reason || '';
     subscription.cancelledAt = new Date();
 
     if (dto.cancelImmediately) {
diff --git a/src/modules/branches/services/branches.service.ts b/src/modules/branches/services/branches.service.ts
index 51fefa8..e06f010 100644
--- a/src/modules/branches/services/branches.service.ts
+++ b/src/modules/branches/services/branches.service.ts
@@ -258,13 +258,17 @@ export class BranchesService {
     }
 
     const assignment = this.assignmentRepository.create({
-      ...dto,
+      userId: dto.userId,
+      branchId: dto.branchId,
       tenantId,
+      assignmentType: (dto.assignmentType || 'primary') as any,
+      branchRole: dto.branchRole as any,
+      permissions: dto.permissions || [],
       validUntil: dto.validUntil ? new Date(dto.validUntil) : undefined,
       createdBy: assignedBy,
-    } as any);
+    });
 
-    return this.assignmentRepository.save(assignment);
+    return this.assignmentRepository.save(assignment) as Promise<UserBranchAssignment>;
   }
 
   async unassignUser(userId: string, branchId: string): Promise<boolean> {
diff --git a/src/modules/financial/financial.controller.ts b/src/modules/financial/financial.controller.ts
index b2d7822..f9b06d7 100644
--- a/src/modules/financial/financial.controller.ts
+++ b/src/modules/financial/financial.controller.ts
@@ -9,37 +9,39 @@ import { taxesService, CreateTaxDto, UpdateTaxDto, TaxFilters } from './taxes.se
 import { AuthenticatedRequest } from '../../shared/middleware/auth.middleware.js';
 import { ValidationError } from '../../shared/errors/index.js';
 
-// Schemas
+// Schemas - Accounts use camelCase DTOs
 const createAccountSchema = z.object({
-  company_id: z.string().uuid(),
+  companyId: z.string().uuid(),
   code: z.string().min(1).max(50),
   name: z.string().min(1).max(255),
-  account_type_id: z.string().uuid(),
-  parent_id: z.string().uuid().optional(),
-  currency_id: z.string().uuid().optional(),
-  is_reconcilable: z.boolean().default(false),
+  accountTypeId: z.string().uuid(),
+  parentId: z.string().uuid().optional(),
+  currencyId: z.string().uuid().optional(),
+  isReconcilable: z.boolean().default(false),
   notes: z.string().optional(),
 });
 
 const updateAccountSchema = z.object({
   name: z.string().min(1).max(255).optional(),
-  parent_id: z.string().uuid().optional().nullable(),
-  currency_id: z.string().uuid().optional().nullable(),
-  is_reconcilable: z.boolean().optional(),
-  is_deprecated: z.boolean().optional(),
+  parentId: z.string().uuid().optional().nullable(),
+  currencyId: z.string().uuid().optional().nullable(),
+  isReconcilable: z.boolean().optional(),
+  isDeprecated: z.boolean().optional(),
   notes: z.string().optional().nullable(),
 });
 
 const accountQuerySchema = z.object({
-  company_id: z.string().uuid().optional(),
-  account_type_id: z.string().uuid().optional(),
-  parent_id: z.string().optional(),
-  is_deprecated: z.coerce.boolean().optional(),
+  companyId: z.string().uuid().optional(),
+  accountTypeId: z.string().uuid().optional(),
+  parentId: z.string().optional(),
+  isDeprecated: z.coerce.boolean().optional(),
   search: z.string().optional(),
   page: z.coerce.number().int().positive().default(1),
   limit: z.coerce.number().int().positive().max(100).default(50),
 });
 
+// Journals and Journal Entries use snake_case DTOs
+
 const createJournalSchema = z.object({
   company_id: z.string().uuid(),
   name: z.string().min(1).max(255),
diff --git a/src/modules/inventory/inventory.controller.ts b/src/modules/inventory/inventory.controller.ts
index de2891a..96d3223 100644
--- a/src/modules/inventory/inventory.controller.ts
+++ b/src/modules/inventory/inventory.controller.ts
@@ -15,19 +15,19 @@ const createProductSchema = z.object({
   code: z.string().max(100).optional(),
   barcode: z.string().max(100).optional(),
   description: z.string().optional(),
-  product_type: z.enum(['storable', 'consumable', 'service']).default('storable'),
+  productType: z.enum(['storable', 'consumable', 'service']).default('storable'),
   tracking: z.enum(['none', 'lot', 'serial']).default('none'),
-  category_id: z.string().uuid().optional(),
-  uom_id: z.string().uuid({ message: 'La unidad de medida es requerida' }),
-  purchase_uom_id: z.string().uuid().optional(),
-  cost_price: z.number().min(0).default(0),
-  list_price: z.number().min(0).default(0),
-  valuation_method: z.enum(['standard', 'fifo', 'average']).default('fifo'),
+  categoryId: z.string().uuid().optional(),
+  uomId: z.string().uuid({ message: 'La unidad de medida es requerida' }),
+  purchaseUomId: z.string().uuid().optional(),
+  costPrice: z.number().min(0).default(0),
+  listPrice: z.number().min(0).default(0),
+  valuationMethod: z.enum(['standard', 'fifo', 'average']).default('fifo'),
   weight: z.number().min(0).optional(),
   volume: z.number().min(0).optional(),
-  can_be_sold: z.boolean().default(true),
-  can_be_purchased: z.boolean().default(true),
-  image_url: z.string().url().max(500).optional(),
+  canBeSold: z.boolean().default(true),
+  canBePurchased: z.boolean().default(true),
+  imageUrl: z.string().url().max(500).optional(),
 });
 
 const updateProductSchema = z.object({
@@ -35,26 +35,26 @@ const updateProductSchema = z.object({
   barcode: z.string().max(100).optional().nullable(),
   description: z.string().optional().nullable(),
   tracking: z.enum(['none', 'lot', 'serial']).optional(),
-  category_id: z.string().uuid().optional().nullable(),
-  uom_id: z.string().uuid().optional(),
-  purchase_uom_id: z.string().uuid().optional().nullable(),
-  cost_price: z.number().min(0).optional(),
-  list_price: z.number().min(0).optional(),
-  valuation_method: z.enum(['standard', 'fifo', 'average']).optional(),
+  categoryId: z.string().uuid().optional().nullable(),
+  uomId: z.string().uuid().optional(),
+  purchaseUomId: z.string().uuid().optional().nullable(),
+  costPrice: z.number().min(0).optional(),
+  listPrice: z.number().min(0).optional(),
+  valuationMethod: z.enum(['standard', 'fifo', 'average']).optional(),
   weight: z.number().min(0).optional().nullable(),
   volume: z.number().min(0).optional().nullable(),
-  can_be_sold: z.boolean().optional(),
-  can_be_purchased: z.boolean().optional(),
-  image_url: z.string().url().max(500).optional().nullable(),
+  canBeSold: z.boolean().optional(),
+  canBePurchased: z.boolean().optional(),
+  imageUrl: z.string().url().max(500).optional().nullable(),
   active: z.boolean().optional(),
 });
 
 const productQuerySchema = z.object({
   search: z.string().optional(),
-  category_id: z.string().uuid().optional(),
-  product_type: z.enum(['storable', 'consumable', 'service']).optional(),
-  can_be_sold: z.coerce.boolean().optional(),
-  can_be_purchased: z.coerce.boolean().optional(),
+  categoryId: z.string().uuid().optional(),
+  productType: z.enum(['storable', 'consumable', 'service']).optional(),
+  canBeSold: z.coerce.boolean().optional(),
+  canBePurchased: z.coerce.boolean().optional(),
   active: z.coerce.boolean().optional(),
   page: z.coerce.number().int().positive().default(1),
   limit: z.coerce.number().int().positive().max(100).default(20),
@@ -62,22 +62,22 @@ const productQuerySchema = z.object({
 
 // Warehouse schemas
 const createWarehouseSchema = z.object({
-  company_id: z.string().uuid({ message: 'La empresa es requerida' }),
+  companyId: z.string().uuid({ message: 'La empresa es requerida' }),
   name: z.string().min(1, 'El nombre es requerido').max(255),
   code: z.string().min(1).max(20),
-  address_id: z.string().uuid().optional(),
-  is_default: z.boolean().default(false),
+  addressId: z.string().uuid().optional(),
+  isDefault: z.boolean().default(false),
 });
 
 const updateWarehouseSchema = z.object({
   name: z.string().min(1).max(255).optional(),
-  address_id: z.string().uuid().optional().nullable(),
-  is_default: z.boolean().optional(),
+  addressId: z.string().uuid().optional().nullable(),
+  isDefault: z.boolean().optional(),
   active: z.boolean().optional(),
 });
 
 const warehouseQuerySchema = z.object({
-  company_id: z.string().uuid().optional(),
+  companyId: z.string().uuid().optional(),
   active: z.coerce.boolean().optional(),
   page: z.coerce.number().int().positive().default(1),
   limit: z.coerce.number().int().positive().max(100).default(50),
@@ -232,7 +232,7 @@ class InventoryController {
         throw new ValidationError('Parámetros de consulta inválidos', queryResult.error.errors);
       }
 
-      const filters: ProductFilters = queryResult.data;
+      const filters = queryResult.data as ProductFilters;
       const result = await productsService.findAll(req.tenantId!, filters);
 
       res.json({
@@ -266,7 +266,7 @@ class InventoryController {
         throw new ValidationError('Datos de producto inválidos', parseResult.error.errors);
       }
 
-      const dto: CreateProductDto = parseResult.data;
+      const dto = parseResult.data as CreateProductDto;
       const product = await productsService.create(dto, req.tenantId!, req.user!.userId);
 
       res.status(201).json({
@@ -286,7 +286,7 @@ class InventoryController {
         throw new ValidationError('Datos de producto inválidos', parseResult.error.errors);
       }
 
-      const dto: UpdateProductDto = parseResult.data;
+      const dto = parseResult.data as UpdateProductDto;
       const product = await productsService.update(req.params.id, dto, req.tenantId!, req.user!.userId);
 
       res.json({
diff --git a/src/modules/inventory/valuation.controller.ts b/src/modules/inventory/valuation.controller.ts
index 01a9c7d..b72a96e 100644
--- a/src/modules/inventory/valuation.controller.ts
+++ b/src/modules/inventory/valuation.controller.ts
@@ -147,7 +147,7 @@ class ValuationController {
         req.user!.tenantId
       );
 
-      const response: ApiResponse = {
+      const response = {
         success: true,
         data: result,
         meta: {
diff --git a/src/modules/notifications/services/notifications.service.ts b/src/modules/notifications/services/notifications.service.ts
index e54d653..4feaa66 100644
--- a/src/modules/notifications/services/notifications.service.ts
+++ b/src/modules/notifications/services/notifications.service.ts
@@ -50,9 +50,10 @@ export class NotificationsService {
     channelType: string,
     tenantId?: string
   ): Promise<NotificationTemplate | null> {
+    const channel = channelType as any;
     const where: FindOptionsWhere<NotificationTemplate>[] = tenantId
-      ? [{ code, channelType, tenantId }, { code, channelType, tenantId: undefined }]
-      : [{ code, channelType }];
+      ? [{ code, channelType: channel, tenantId }, { code, channelType: channel, tenantId: undefined as any }]
+      : [{ code, channelType: channel }];
 
     return this.templateRepository.findOne({
       where,
diff --git a/src/modules/payment-terminals/services/transactions.service.ts b/src/modules/payment-terminals/services/transactions.service.ts
index ed574d0..146fde5 100644
--- a/src/modules/payment-terminals/services/transactions.service.ts
+++ b/src/modules/payment-terminals/services/transactions.service.ts
@@ -90,12 +90,12 @@ export class TransactionsService {
 
       // Update transaction with result
       transaction.status = providerResult.status;
-      transaction.externalTransactionId = providerResult.externalTransactionId;
-      transaction.paymentMethod = providerResult.paymentMethod;
-      transaction.cardBrand = providerResult.cardBrand;
-      transaction.cardLastFour = providerResult.cardLastFour;
-      transaction.receiptUrl = providerResult.receiptUrl;
-      transaction.providerResponse = providerResult.rawResponse;
+      transaction.externalTransactionId = providerResult.externalTransactionId || '';
+      transaction.paymentMethod = providerResult.paymentMethod || transaction.paymentMethod;
+      transaction.cardBrand = providerResult.cardBrand || '';
+      transaction.cardLastFour = providerResult.cardLastFour || '';
+      transaction.receiptUrl = providerResult.receiptUrl || '';
+      transaction.providerResponse = providerResult.rawResponse || {};
 
       if (providerResult.status === 'completed') {
         transaction.completedAt = new Date();
@@ -105,7 +105,7 @@ export class TransactionsService {
           healthStatus: 'healthy',
         });
       } else if (providerResult.status === 'failed') {
-        transaction.failureReason = providerResult.error;
+        transaction.failureReason = providerResult.error || '';
       }
 
       await this.transactionRepository.save(transaction);
@@ -390,10 +390,9 @@ export class TransactionsService {
     if (!this.circuitBreakers.has(terminalId)) {
       this.circuitBreakers.set(
         terminalId,
-        new CircuitBreaker({
-          name: `terminal-${terminalId}`,
+        new CircuitBreaker(`terminal-${terminalId}`, {
           failureThreshold: 3,
-          successThreshold: 2,
+          halfOpenRequests: 2,
           resetTimeout: 30000, // 30 seconds
         })
       );