690406:2310 Done Task BE-ERR-01

backend/src/common/common.module.ts

@@ -7,7 +7,7 @@ import { CryptoService } from './services/crypto.service';
 import { RequestContextService } from './services/request-context.service';
 import { UuidResolverService } from './services/uuid-resolver.service';
 import { APP_FILTER, APP_INTERCEPTOR } from '@nestjs/core';
-import { HttpExceptionFilter } from './exceptions/http-exception.filter';
+import { GlobalExceptionFilter } from './filters/global-exception.filter';
 import { TransformInterceptor } from './interceptors/transform.interceptor';
 // import { IdempotencyInterceptor } from './interceptors/idempotency.interceptor'; // นำเข้าถ้าต้องการใช้ Global
 
@@ -21,7 +21,7 @@ import { TransformInterceptor } from './interceptors/transform.interceptor';
     // Register Global Filter & Interceptor ที่นี่ หรือใน AppModule ก็ได้
     {
       provide: APP_FILTER,
-      useClass: HttpExceptionFilter,
+      useClass: GlobalExceptionFilter,
     },
     {
       provide: APP_INTERCEPTOR,

backend/src/common/exceptions/base.exception.ts

@@ -0,0 +1,235 @@
+// File: src/common/exceptions/base.exception.ts
+// ADR-007: Exception hierarchy สำหรับ Layered Error Handling
+
+import { HttpException, HttpStatus } from '@nestjs/common';
+
+// ประเภทของ Error ที่ระบบรองรับ
+export enum ErrorType {
+  VALIDATION = 'VALIDATION',
+  BUSINESS_RULE = 'BUSINESS_RULE',
+  PERMISSION_DENIED = 'PERMISSION_DENIED',
+  NOT_FOUND = 'NOT_FOUND',
+  CONFLICT = 'CONFLICT',
+  INTERNAL_ERROR = 'INTERNAL_ERROR',
+  DATABASE_ERROR = 'DATABASE_ERROR',
+  EXTERNAL_SERVICE = 'EXTERNAL_SERVICE',
+  INFRASTRUCTURE = 'INFRASTRUCTURE',
+}
+
+// ระดับความรุนแรงของ Error
+export enum ErrorSeverity {
+  LOW = 'LOW', // ผู้ใช้ทำผิด แก้ไขง่าย
+  MEDIUM = 'MEDIUM', // ละเมิดกฎทางธุรกิจ ต้องดำเนินการ
+  HIGH = 'HIGH', // ปัญหาระบบ อาจต้องติดต่อ Support
+  CRITICAL = 'CRITICAL', // ระบบล้มเหลว ต้องแก้ไขทันที
+}
+
+// รายละเอียด Validation Error แต่ละ Field
+export interface ValidationErrorDetail {
+  field: string;
+  message: string;
+  value?: unknown;
+}
+
+// แปลง ErrorType เป็น HTTP Status Code
+export function getStatusCode(type: ErrorType): number {
+  switch (type) {
+    case ErrorType.VALIDATION:
+      return HttpStatus.BAD_REQUEST;
+    case ErrorType.BUSINESS_RULE:
+      return HttpStatus.UNPROCESSABLE_ENTITY;
+    case ErrorType.PERMISSION_DENIED:
+      return HttpStatus.FORBIDDEN;
+    case ErrorType.NOT_FOUND:
+      return HttpStatus.NOT_FOUND;
+    case ErrorType.CONFLICT:
+      return HttpStatus.CONFLICT;
+    case ErrorType.INTERNAL_ERROR:
+    case ErrorType.DATABASE_ERROR:
+    case ErrorType.EXTERNAL_SERVICE:
+    case ErrorType.INFRASTRUCTURE:
+      return HttpStatus.INTERNAL_SERVER_ERROR;
+    default:
+      return HttpStatus.INTERNAL_SERVER_ERROR;
+  }
+}
+
+// รูปแบบ Payload ของ Error Response
+export interface ErrorPayload {
+  type: ErrorType;
+  code: string;
+  message: string;
+  severity: ErrorSeverity;
+  timestamp: string;
+  recoveryActions?: string[];
+  technicalMessage?: string;
+  details?: ValidationErrorDetail[] | Record<string, unknown>;
+}
+
+// Base Exception ที่ทุก Custom Exception ต้อง extends
+export abstract class BaseException extends HttpException {
+  public readonly httpStatus: number;
+
+  constructor(
+    public readonly type: ErrorType,
+    public readonly code: string,
+    public readonly technicalMessage: string,
+    public readonly userMessage?: string,
+    public readonly severity: ErrorSeverity = ErrorSeverity.MEDIUM,
+    public readonly details?: ValidationErrorDetail[] | Record<string, unknown>,
+    public readonly recoveryActions?: string[]
+  ) {
+    const httpStatus = getStatusCode(type);
+
+    const payload: ErrorPayload = {
+      type,
+      code,
+      message: userMessage || technicalMessage,
+      severity,
+      timestamp: new Date().toISOString(),
+      ...(recoveryActions && { recoveryActions }),
+      ...(process.env['NODE_ENV'] !== 'production' && {
+        technicalMessage,
+        ...(details && { details }),
+      }),
+    };
+
+    super({ error: payload }, httpStatus);
+    this.httpStatus = httpStatus;
+  }
+}
+
+// Validation Errors (400) - ข้อมูล Input ผิดพลาด
+export class ValidationException extends BaseException {
+  constructor(message: string, details?: ValidationErrorDetail[]) {
+    super(
+      ErrorType.VALIDATION,
+      'VALIDATION_ERROR',
+      message,
+      'ข้อมูลที่กรอกไม่ถูกต้อง กรุณาตรวจสอบและลองใหม่',
+      ErrorSeverity.LOW,
+      details,
+      ['ตรวจสอบข้อมูลที่กรอก', 'แก้ไขข้อมูลที่ผิดพลาด', 'ลองใหม่อีกครั้ง']
+    );
+  }
+}
+
+// Business Rule Errors (422) - ละเมิดกฎทางธุรกิจ
+export class BusinessException extends BaseException {
+  constructor(
+    code: string,
+    message: string,
+    userMessage?: string,
+    recoveryActions?: string[]
+  ) {
+    super(
+      ErrorType.BUSINESS_RULE,
+      code,
+      message,
+      userMessage || 'ไม่สามารถดำเนินการได้เนื่องจากเงื่อนไขทางธุรกิจ',
+      ErrorSeverity.MEDIUM,
+      undefined,
+      recoveryActions || ['ติดต่อผู้ดูแลระบบ', 'ตรวจสอบเงื่อนไขการดำเนินการ']
+    );
+  }
+}
+
+// Not Found Errors (404) - ไม่พบข้อมูล
+export class NotFoundException extends BaseException {
+  constructor(resource: string, identifier?: string) {
+    super(
+      ErrorType.NOT_FOUND,
+      'NOT_FOUND',
+      `${resource}${identifier ? ` with identifier "${identifier}"` : ''} not found`,
+      `ไม่พบ${resource}ที่ค้นหา`,
+      ErrorSeverity.LOW,
+      undefined,
+      ['ตรวจสอบ ID/UUID ที่ระบุ', 'ค้นหาข้อมูลจากรายการ']
+    );
+  }
+}
+
+// Permission Errors (403) - ไม่มีสิทธิ์
+export class PermissionException extends BaseException {
+  constructor(resource: string, action: string) {
+    super(
+      ErrorType.PERMISSION_DENIED,
+      'PERMISSION_DENIED',
+      `User lacks permission for "${action}" on "${resource}"`,
+      `คุณไม่มีสิทธิ์ดำเนินการ "${action}" บน "${resource}"`,
+      ErrorSeverity.MEDIUM,
+      { resource, action },
+      ['ติดต่อผู้ดูแลระบบเพื่อขอสิทธิ์', 'ลองใช้บัญชีที่มีสิทธิ์']
+    );
+  }
+}
+
+// Conflict Errors (409) - ข้อมูลซ้ำ / ขัดแย้ง
+export class ConflictException extends BaseException {
+  constructor(
+    code: string,
+    message: string,
+    userMessage?: string,
+    recoveryActions?: string[]
+  ) {
+    super(
+      ErrorType.CONFLICT,
+      code,
+      message,
+      userMessage || 'ข้อมูลซ้ำกันหรือขัดแย้งกับข้อมูลที่มีอยู่',
+      ErrorSeverity.MEDIUM,
+      undefined,
+      recoveryActions || ['ตรวจสอบข้อมูลที่มีอยู่', 'แก้ไขข้อมูลที่ขัดแย้ง']
+    );
+  }
+}
+
+// Workflow Errors (422) - ข้อผิดพลาดจาก Workflow Engine
+export class WorkflowException extends BaseException {
+  constructor(
+    code: string,
+    message: string,
+    userMessage?: string,
+    recoveryActions?: string[]
+  ) {
+    super(
+      ErrorType.BUSINESS_RULE,
+      code,
+      message,
+      userMessage || 'ไม่สามารถดำเนินการ Workflow ได้ในสถานะปัจจุบัน',
+      ErrorSeverity.MEDIUM,
+      undefined,
+      recoveryActions || ['ตรวจสอบสถานะเอกสาร', 'ดำเนินการอื่นที่อนุญาต']
+    );
+  }
+}
+
+// System/Infrastructure Errors (500) - ปัญหาระบบ
+export class SystemException extends BaseException {
+  constructor(message: string, details?: Record<string, unknown>) {
+    super(
+      ErrorType.INTERNAL_ERROR,
+      'INTERNAL_ERROR',
+      message,
+      'เกิดข้อผิดพลาดในระบบ กรุณาลองใหม่ภายหลัง',
+      ErrorSeverity.HIGH,
+      details,
+      ['ลองใหม่อีกครั้ง', 'ติดต่อผู้ดูแลระบบหากยังพบปัญหา']
+    );
+  }
+}
+
+// Database Errors (500) - ปัญหาฐานข้อมูล
+export class DatabaseException extends BaseException {
+  constructor(message: string, details?: Record<string, unknown>) {
+    super(
+      ErrorType.DATABASE_ERROR,
+      'DATABASE_ERROR',
+      message,
+      'เกิดข้อผิดพลาดของฐานข้อมูล กรุณาลองใหม่ภายหลัง',
+      ErrorSeverity.HIGH,
+      details,
+      ['ลองใหม่ภายหลัง', 'แจ้งผู้ดูแลระบบหากยังพบปัญหา']
+    );
+  }
+}

backend/src/common/exceptions/index.ts

@@ -0,0 +1,19 @@
+// File: src/common/exceptions/index.ts
+// Barrel export สำหรับ Exception Hierarchy ทั้งหมด
+
+export {
+  ErrorType,
+  ErrorSeverity,
+  getStatusCode,
+  BaseException,
+  ValidationException,
+  BusinessException,
+  NotFoundException,
+  PermissionException,
+  ConflictException,
+  WorkflowException,
+  SystemException,
+  DatabaseException,
+} from './base.exception';
+
+export type { ValidationErrorDetail, ErrorPayload } from './base.exception';

backend/src/common/filters/global-exception.filter.ts

@@ -0,0 +1,216 @@
+// File: src/common/filters/global-exception.filter.ts
+// ADR-007: Global Exception Filter พร้อม Layered Error Processing
+
+import {
+  ExceptionFilter,
+  Catch,
+  ArgumentsHost,
+  HttpException,
+  HttpStatus,
+  Injectable,
+  Logger,
+} from '@nestjs/common';
+import { Response } from 'express';
+import { RequestWithUser } from '../interfaces/request-with-user.interface';
+import {
+  BaseException,
+  ErrorType,
+  ErrorSeverity,
+  ErrorPayload,
+} from '../exceptions/base.exception';
+
+// รูปแบบ Error Response ที่ส่งกลับ Client
+interface ErrorResponse {
+  error: ErrorPayload & { statusCode: number };
+}
+
+// ข้อมูล Log สำหรับ Error
+interface ErrorLogData {
+  path: string;
+  method: string;
+  userId?: number;
+  ip: string;
+  userAgent: string;
+  exception: {
+    name: string;
+    message: string;
+    stack?: string;
+    details?: unknown;
+  };
+}
+
+@Injectable()
+@Catch()
+export class GlobalExceptionFilter implements ExceptionFilter {
+  private readonly logger = new Logger(GlobalExceptionFilter.name);
+
+  catch(exception: unknown, host: ArgumentsHost): void {
+    const ctx = host.switchToHttp();
+    const response = ctx.getResponse<Response>();
+    const request = ctx.getRequest<RequestWithUser>();
+
+    let errorResponse: ErrorResponse;
+    let httpStatus: number;
+
+    if (exception instanceof BaseException) {
+      // จัดการ Custom Exception ของเรา (ADR-007)
+      const payload = exception.getResponse() as { error: ErrorPayload };
+      httpStatus = exception.httpStatus;
+      errorResponse = {
+        error: {
+          ...payload.error,
+          statusCode: httpStatus,
+        },
+      };
+      this.logError(
+        exception,
+        request,
+        exception.severity === ErrorSeverity.CRITICAL
+      );
+    } else if (exception instanceof HttpException) {
+      // จัดการ NestJS Built-in Exceptions
+      httpStatus = exception.getStatus();
+      const exceptionResponse = exception.getResponse();
+
+      // แปลง NestJS exception response เป็น user-friendly message
+      let technicalDetail: unknown = exceptionResponse;
+      if (typeof exceptionResponse === 'object' && exceptionResponse !== null) {
+        technicalDetail = exceptionResponse;
+      }
+
+      errorResponse = {
+        error: {
+          type: this.mapStatusToErrorType(httpStatus),
+          code: 'HTTP_ERROR',
+          message: this.mapStatusToUserMessage(httpStatus),
+          severity:
+            httpStatus >= 500 ? ErrorSeverity.HIGH : ErrorSeverity.MEDIUM,
+          timestamp: new Date().toISOString(),
+          statusCode: httpStatus,
+          recoveryActions: this.mapStatusToRecoveryActions(httpStatus),
+          ...(process.env['NODE_ENV'] !== 'production' && {
+            technicalMessage: exception.message,
+            details: technicalDetail as Record<string, unknown>,
+          }),
+        },
+      };
+      this.logError(exception, request, httpStatus >= 500);
+    } else {
+      // จัดการ Unexpected Errors (ไม่รู้ประเภท)
+      httpStatus = HttpStatus.INTERNAL_SERVER_ERROR;
+      errorResponse = {
+        error: {
+          type: ErrorType.INTERNAL_ERROR,
+          code: 'UNEXPECTED_ERROR',
+          message: 'เกิดข้อผิดพลาดที่ไม่คาดคิด กรุณาลองใหม่ภายหลัง',
+          severity: ErrorSeverity.CRITICAL,
+          timestamp: new Date().toISOString(),
+          statusCode: httpStatus,
+          recoveryActions: [
+            'ลองใหม่อีกครั้ง',
+            'ติดต่อผู้ดูแลระบบหากยังพบปัญหา',
+          ],
+        },
+      };
+      this.logError(exception, request, true);
+    }
+
+    response.status(httpStatus).json(errorResponse);
+  }
+
+  // Logging แยกตามความรุนแรง
+  private logError(
+    exception: unknown,
+    request: RequestWithUser,
+    isCritical: boolean
+  ): void {
+    const err =
+      exception instanceof Error ? exception : new Error(String(exception));
+
+    const logData: ErrorLogData = {
+      path: request.url,
+      method: request.method,
+      userId: request.user?.user_id,
+      ip: request.ip ?? 'unknown',
+      userAgent: (request.headers['user-agent'] as string) ?? 'unknown',
+      exception: {
+        name: err.name,
+        message: err.message,
+        stack: err.stack,
+        details:
+          exception instanceof BaseException ? exception.details : undefined,
+      },
+    };
+
+    if (isCritical) {
+      this.logger.error('Critical error occurred', JSON.stringify(logData));
+    } else {
+      this.logger.warn('Error occurred', JSON.stringify(logData));
+    }
+  }
+
+  // แปลง HTTP Status เป็น ErrorType
+  private mapStatusToErrorType(status: number): ErrorType {
+    switch (status) {
+      case 400:
+        return ErrorType.VALIDATION;
+      case 401:
+      case 403:
+        return ErrorType.PERMISSION_DENIED;
+      case 404:
+        return ErrorType.NOT_FOUND;
+      case 409:
+        return ErrorType.CONFLICT;
+      case 422:
+        return ErrorType.BUSINESS_RULE;
+      default:
+        return ErrorType.INTERNAL_ERROR;
+    }
+  }
+
+  // แปลง HTTP Status เป็น User-friendly Message (ภาษาไทย)
+  private mapStatusToUserMessage(status: number): string {
+    switch (status) {
+      case 400:
+        return 'ข้อมูลที่ส่งมาไม่ถูกต้อง กรุณาตรวจสอบและลองใหม่';
+      case 401:
+        return 'กรุณาเข้าสู่ระบบก่อนใช้งาน';
+      case 403:
+        return 'คุณไม่มีสิทธิ์ในการดำเนินการนี้';
+      case 404:
+        return 'ไม่พบข้อมูลที่ร้องขอ';
+      case 409:
+        return 'ข้อมูลซ้ำกันหรือมีความขัดแย้ง';
+      case 422:
+        return 'ไม่สามารถดำเนินการได้เนื่องจากเงื่อนไขทางธุรกิจ';
+      case 429:
+        return 'คำขอมากเกินไป กรุณารอสักครู่แล้วลองใหม่';
+      default:
+        return 'เกิดข้อผิดพลาดในระบบ กรุณาลองใหม่ภายหลัง';
+    }
+  }
+
+  // Recovery Actions สำหรับแต่ละ HTTP Status
+  private mapStatusToRecoveryActions(status: number): string[] {
+    switch (status) {
+      case 400:
+        return [
+          'ตรวจสอบข้อมูลที่กรอก',
+          'แก้ไขข้อมูลที่ผิดพลาด',
+          'ลองใหม่อีกครั้ง',
+        ];
+      case 401:
+        return ['เข้าสู่ระบบ', 'ตรวจสอบ Session ที่หมดอายุ'];
+      case 403:
+        return ['ติดต่อผู้ดูแลระบบเพื่อขอสิทธิ์', 'ลองใช้บัญชีที่มีสิทธิ์'];
+      case 404:
+        return ['ตรวจสอบ ID/UUID ที่ระบุ', 'ค้นหาข้อมูลจากรายการ'];
+      case 409:
+        return ['ตรวจสอบข้อมูลที่มีอยู่', 'แก้ไขข้อมูลที่ขัดแย้ง'];
+      case 429:
+        return ['รอสักครู่แล้วลองใหม่'];
+      default:
+        return ['ลองใหม่อีกครั้ง', 'ติดต่อผู้ดูแลระบบหากยังพบปัญหา'];
+    }
+  }
+}

backend/src/modules/circulation/circulation.service.ts

@@ -1,9 +1,9 @@
+import { Injectable } from '@nestjs/common';
 import {
-  Injectable,
   NotFoundException,
-  BadRequestException,
-  ForbiddenException,
-} from '@nestjs/common';
+  PermissionException,
+  ValidationException,
+} from '../../common/exceptions';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository, DataSource } from 'typeorm';
 
@@ -53,15 +53,18 @@ export class CirculationService {
         user.user_id
       );
       if (!canManageAll) {
-        throw new ForbiddenException(
-          'You do not have permission to create documents on behalf of other organizations.'
+        throw new PermissionException(
+          'circulation',
+          'create on behalf of other organization'
         );
       }
       userOrgId = resolvedOriginatorId;
     }
 
     if (!userOrgId) {
-      throw new BadRequestException('User must belong to an organization');
+      throw new ValidationException(
+        'User must belong to an organization to create a circulation'
+      );
     }
 
     const queryRunner = this.dataSource.createQueryRunner();
@@ -195,11 +198,12 @@ export class CirculationService {
       relations: ['circulation'],
     });
 
-    if (!routing) throw new NotFoundException('Routing task not found');
+    if (!routing)
+      throw new NotFoundException('Routing task', String(routingId));
 
     // Check Permission: คนทำต้องเป็นเจ้าของ Task
     if (routing.assignedTo !== user.user_id) {
-      throw new ForbiddenException('You are not assigned to this task');
+      throw new PermissionException('circulation routing task', 'process');
     }
 
     // Update Routing

backend/src/modules/correspondence/correspondence.service.spec.ts

@@ -1,7 +1,7 @@
 import { Test, TestingModule } from '@nestjs/testing';
 import { getRepositoryToken } from '@nestjs/typeorm';
 import { DataSource, Repository } from 'typeorm';
-import { ForbiddenException } from '@nestjs/common';
+import { PermissionException } from '../../common/exceptions';
 import { CorrespondenceService } from './correspondence.service';
 import { Correspondence } from './entities/correspondence.entity';
 import { CorrespondenceRevision } from './entities/correspondence-revision.entity';
@@ -260,7 +260,7 @@ describe('CorrespondenceService', () => {
 
       await expect(
         service.update(2, { subject: 'Should Fail' }, mockUser)
-      ).rejects.toThrow(ForbiddenException);
+      ).rejects.toThrow(PermissionException);
     });
 
     it('should NOT regenerate number if critical fields unchanged', async () => {

backend/src/modules/correspondence/correspondence.service.ts

@@ -1,13 +1,13 @@
 // File: src/modules/correspondence/correspondence.service.ts
 
+import { Injectable, Logger } from '@nestjs/common';
 import {
-  Injectable,
+  BusinessException,
   NotFoundException,
-  BadRequestException,
-  InternalServerErrorException,
-  ForbiddenException,
-  Logger,
-} from '@nestjs/common';
+  PermissionException,
+  SystemException,
+  ValidationException,
+} from '../../common/exceptions';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository, DataSource } from 'typeorm';
 
@@ -125,7 +125,7 @@ export class CorrespondenceService {
       }
 
       if (!userOrgId) {
-        throw new BadRequestException(
+        throw new ValidationException(
           'User must belong to an organization to create documents'
         );
       }
@@ -139,14 +139,17 @@ export class CorrespondenceService {
     // Check if it's internal communication
     if (createDto.isInternal) {
       // Internal communications should use Circulation instead
-      throw new BadRequestException(
-        'Internal communications should use Circulation Sheet instead of Correspondence'
+      throw new BusinessException(
+        'INVALID_DOCUMENT_TYPE',
+        'Internal communications should use Circulation Sheet instead of Correspondence',
+        'การสื่อสารภายในควรใช้ Circulation Sheet แทน Correspondence',
+        ['ใช้ Circulation Sheet สำหรับการสื่อสารภายในองค์กร']
       );
     }
 
     // Validate recipients
     if (!createDto.recipients || createDto.recipients.length === 0) {
-      throw new BadRequestException(
+      throw new ValidationException(
         'At least one recipient (TO or CC) is required'
       );
     }
@@ -155,7 +158,7 @@ export class CorrespondenceService {
     const ccRecipients = createDto.recipients.filter((r) => r.type === 'CC');
 
     if (toRecipients.length === 0 && ccRecipients.length === 0) {
-      throw new BadRequestException(
+      throw new ValidationException(
         'At least one TO or CC recipient is required'
       );
     }
@@ -167,8 +170,11 @@ export class CorrespondenceService {
       );
 
       if (recipientOrgId === originatorOrgId) {
-        throw new BadRequestException(
-          'Cannot send correspondence to your own organization. Use Circulation Sheet for internal communication.'
+        throw new BusinessException(
+          'CORRESPONDENCE_TO_SELF',
+          'Cannot send correspondence to your own organization',
+          'ไม่สามารถส่งเอกสารถึงองค์กรของตัวเองได้ ใช้ Circulation Sheet แทน',
+          ['ใช้ Circulation Sheet สำหรับการสื่อสารภายใน']
         );
       }
     }
@@ -199,15 +205,14 @@ export class CorrespondenceService {
     const type = await this.typeRepo.findOne({
       where: { id: createDto.typeId },
     });
-    if (!type) throw new NotFoundException('Document Type not found');
+    if (!type)
+      throw new NotFoundException('Document Type', String(createDto.typeId));
 
     const statusDraft = await this.statusRepo.findOne({
       where: { statusCode: 'DRAFT' },
     });
     if (!statusDraft) {
-      throw new InternalServerErrorException(
-        'Status DRAFT not found in Master Data'
-      );
+      throw new SystemException('Status DRAFT not found in Master Data');
     }
 
     let userOrgId = user.primaryOrganizationId;
@@ -225,15 +230,16 @@ export class CorrespondenceService {
         user.user_id
       );
       if (!canManageAll) {
-        throw new ForbiddenException(
-          'You do not have permission to create documents on behalf of other organizations.'
+        throw new PermissionException(
+          'correspondence',
+          'create on behalf of other organization'
         );
       }
       userOrgId = resolvedOriginatorId;
     }
 
     if (!userOrgId) {
-      throw new BadRequestException(
+      throw new ValidationException(
         'User must belong to an organization to create documents'
       );
     }
@@ -505,7 +511,7 @@ export class CorrespondenceService {
     });
 
     if (!correspondence) {
-      throw new NotFoundException(`Correspondence with ID ${id} not found`);
+      throw new NotFoundException('Correspondence', String(id));
     }
     return correspondence;
   }
@@ -533,9 +539,7 @@ export class CorrespondenceService {
       .getOne();
 
     if (!correspondence) {
-      throw new NotFoundException(
-        `Correspondence with UUID ${publicId} not found`
-      );
+      throw new NotFoundException('Correspondence', publicId);
     }
     return correspondence;
   }
@@ -548,11 +552,15 @@ export class CorrespondenceService {
     });
 
     if (!source || !target) {
-      throw new NotFoundException('Source or Target correspondence not found');
+      throw new NotFoundException('Source or Target correspondence');
     }
 
     if (source.id === target.id) {
-      throw new BadRequestException('Cannot reference self');
+      throw new BusinessException(
+        'SELF_REFERENCE',
+        'Cannot reference self',
+        'ไม่สามารถอ้างอิงเอกสารเดียวกันได้'
+      );
     }
 
     const exists = await this.referenceRepo.findOne({
@@ -581,7 +589,7 @@ export class CorrespondenceService {
     });
 
     if (result.affected === 0) {
-      throw new NotFoundException('Reference not found');
+      throw new NotFoundException('Reference');
     }
   }
 
@@ -598,14 +606,14 @@ export class CorrespondenceService {
       where: { id },
     });
     if (!correspondence) {
-      throw new NotFoundException(`Correspondence ${id} not found`);
+      throw new NotFoundException('Correspondence', String(id));
     }
 
     const tag = await this.dataSource.manager.findOne(Tag, {
       where: { id: tagId },
     });
     if (!tag) {
-      throw new NotFoundException(`Tag ${tagId} not found`);
+      throw new NotFoundException('Tag', String(tagId));
     }
 
     const exists = await this.tagRepo.findOne({
@@ -620,7 +628,7 @@ export class CorrespondenceService {
   async removeTag(id: number, tagId: number) {
     const result = await this.tagRepo.delete({ correspondenceId: id, tagId });
     if (result.affected === 0) {
-      throw new NotFoundException('Tag assignment not found');
+      throw new NotFoundException('Tag assignment');
     }
   }
 
@@ -649,9 +657,7 @@ export class CorrespondenceService {
     });
 
     if (!revision) {
-      throw new NotFoundException(
-        `Current revision for correspondence ${id} not found`
-      );
+      throw new NotFoundException('Current revision', `correspondence:${id}`);
     }
 
     // 2. Check Permission
@@ -669,9 +675,7 @@ export class CorrespondenceService {
           permissions.includes('system.manage_all');
 
         if (!canEditSubmittedOrLater) {
-          throw new ForbiddenException(
-            'Only Org Admin or Superadmin can edit non-draft correspondences'
-          );
+          throw new PermissionException('correspondence', 'edit non-draft');
         }
       }
     }
@@ -699,7 +703,7 @@ export class CorrespondenceService {
     // 3. Check if number regeneration is needed (only for DRAFT status)
     const oldCorr = revision.correspondence;
     if (!oldCorr) {
-      throw new InternalServerErrorException(
+      throw new SystemException(
         'Correspondence relation not loaded for revision'
       );
     }
@@ -734,7 +738,7 @@ export class CorrespondenceService {
         const type = await this.typeRepo.findOne({ where: { id: typeId } });
 
         if (!type) {
-          throw new NotFoundException('Document Type not found');
+          throw new NotFoundException('Document Type', String(typeId));
         }
 
         // Get recipient org code for number generation
@@ -898,7 +902,8 @@ export class CorrespondenceService {
     const type = await this.typeRepo.findOne({
       where: { id: createDto.typeId },
     });
-    if (!type) throw new NotFoundException('Document Type not found');
+    if (!type)
+      throw new NotFoundException('Document Type', String(createDto.typeId));
 
     let userOrgId = user.primaryOrganizationId;
     if (!userOrgId) {
@@ -953,9 +958,7 @@ export class CorrespondenceService {
       permissions.includes('system.manage_all');
 
     if (!canCancel) {
-      throw new ForbiddenException(
-        'Only administrators can cancel correspondences'
-      );
+      throw new PermissionException('correspondence', 'cancel');
     }
 
     // Check if there are any active circulations
@@ -981,7 +984,7 @@ export class CorrespondenceService {
     });
 
     if (!currentRevision) {
-      throw new NotFoundException('Current revision not found');
+      throw new NotFoundException('Current revision');
     }
 
     // Get cancelled status
@@ -990,7 +993,7 @@ export class CorrespondenceService {
     });
 
     if (!cancelledStatus) {
-      throw new InternalServerErrorException('CANCELLED status not found');
+      throw new SystemException('CANCELLED status not found in Master Data');
     }
 
     const queryRunner = this.dataSource.createQueryRunner();

backend/src/modules/dashboard/dashboard.service.ts

@@ -24,7 +24,10 @@ import {
 } from './dto';
 import { Project } from '../project/entities/project.entity';
 import { UserAssignment } from '../user/entities/user-assignment.entity';
-import { ForbiddenException, NotFoundException } from '@nestjs/common';
+import {
+  NotFoundException,
+  PermissionException,
+} from '../../common/exceptions';
 
 @Injectable()
 export class DashboardService {
@@ -58,7 +61,7 @@ export class DashboardService {
     });
 
     if (!project) {
-      throw new NotFoundException(`Project with ID ${projectId} not found`);
+      throw new NotFoundException('Project', String(projectId));
     }
 
     // 2. ตรวจสอบสิทธิ (UserAssignment)
@@ -82,9 +85,7 @@ export class DashboardService {
       this.logger.warn(
         `User ${userId} attempted to access project ${projectId} without assignment`
       );
-      throw new ForbiddenException(
-        `You do not have access to project ${projectId}`
-      );
+      throw new PermissionException('project', 'view');
     }
 
     return project.id;

backend/src/modules/document-numbering/services/document-numbering.service.ts

@@ -1,4 +1,5 @@
-import { Injectable, Logger, BadRequestException } from '@nestjs/common';
+import { Injectable, Logger } from '@nestjs/common';
+import { BusinessException } from '../../../common/exceptions';
 import { InjectRepository, InjectEntityManager } from '@nestjs/typeorm';
 import { Repository, EntityManager, IsNull, Equal } from 'typeorm';
 import { ConfigService } from '@nestjs/config';
@@ -318,8 +319,11 @@ export class DocumentNumberingService {
   async setCounterValue(id: number, sequence: number) {
     await Promise.resolve(id); // satisfy unused
     await Promise.resolve(sequence);
-    throw new BadRequestException(
-      'Updating counter by single ID is not supported with composite keys. Use manualOverride.'
+    throw new BusinessException(
+      'COUNTER_UPDATE_NOT_SUPPORTED',
+      'Updating counter by single ID is not supported with composite keys',
+      'ไม่รองรับการอัปเดต Counter แบบ Single ID กรุณาใช้ manualOverride',
+      ['ใช้ manualOverride แทน']
     );
   }
 

backend/src/modules/json-schema/json-schema.service.ts

@@ -1,13 +1,12 @@
 // File: src/modules/json-schema/json-schema.service.ts
 // บันทึกการแก้ไข: Fix TS2345 (undefined check)
 
+import { Injectable, Logger, OnModuleInit } from '@nestjs/common';
 import {
-  BadRequestException,
-  Injectable,
-  Logger,
+  BusinessException,
   NotFoundException,
-  OnModuleInit,
-} from '@nestjs/common';
+  ValidationException,
+} from '../../common/exceptions';
 import { InjectRepository } from '@nestjs/typeorm';
 import Ajv, { ValidateFunction } from 'ajv';
 import addFormats from 'ajv-formats';
@@ -101,7 +100,7 @@ export class JsonSchemaService implements OnModuleInit {
     try {
       this.ajv.compile(createDto.schemaDefinition);
     } catch (error: unknown) {
-      throw new BadRequestException(
+      throw new ValidationException(
         `Invalid JSON Schema format: ${error instanceof Error ? error.message : String(error)}`
       );
     }
@@ -207,7 +206,7 @@ export class JsonSchemaService implements OnModuleInit {
   async findOne(id: number): Promise<JsonSchema> {
     const schema = await this.jsonSchemaRepository.findOne({ where: { id } });
     if (!schema) {
-      throw new NotFoundException(`JsonSchema with ID ${id} not found`);
+      throw new NotFoundException('JsonSchema', String(id));
     }
     return schema;
   }
@@ -224,9 +223,7 @@ export class JsonSchemaService implements OnModuleInit {
     });
 
     if (!schema) {
-      throw new NotFoundException(
-        `JsonSchema '${code}' version ${version} not found`
-      );
+      throw new NotFoundException('JsonSchema', `${code}@v${version}`);
     }
     return schema;
   }
@@ -241,9 +238,7 @@ export class JsonSchemaService implements OnModuleInit {
     });
 
     if (!schema) {
-      throw new NotFoundException(
-        `Active JsonSchema with code '${code}' not found`
-      );
+      throw new NotFoundException('Active JsonSchema', code);
     }
     return schema;
   }
@@ -333,8 +328,10 @@ export class JsonSchemaService implements OnModuleInit {
         validate = this.ajv.compile(schema.schemaDefinition);
         this.validators.set(schemaCode, validate);
       } catch (error: unknown) {
-        throw new BadRequestException(
-          `Invalid Schema Definition for '${schemaCode}': ${error instanceof Error ? error.message : String(error)}`
+        throw new BusinessException(
+          'INVALID_SCHEMA_DEFINITION',
+          `Invalid Schema Definition for '${schemaCode}': ${error instanceof Error ? error.message : String(error)}`,
+          'Schema Definition ไม่ถูกต้อง'
         );
       }
     }
@@ -353,7 +350,7 @@ export class JsonSchemaService implements OnModuleInit {
       const errorMsg = result.errors
         .map((e) => `${e.field}: ${e.message}`)
         .join(', ');
-      throw new BadRequestException(`JSON Validation Failed: ${errorMsg}`);
+      throw new ValidationException(`JSON Validation Failed: ${errorMsg}`);
     }
     return true;
   }
@@ -372,7 +369,7 @@ export class JsonSchemaService implements OnModuleInit {
       try {
         this.ajv.compile(updateDto.schemaDefinition);
       } catch (error: unknown) {
-        throw new BadRequestException(
+        throw new ValidationException(
           `Invalid JSON Schema format: ${error instanceof Error ? error.message : String(error)}`
         );
       }

backend/src/modules/json-schema/services/schema-migration.service.ts

@@ -1,5 +1,9 @@
 // File: src/modules/json-schema/services/schema-migration.service.ts
-import { Injectable, Logger, BadRequestException } from '@nestjs/common';
+import { Injectable, Logger } from '@nestjs/common';
+import {
+  BusinessException,
+  NotFoundException,
+} from '../../../common/exceptions';
 import { DataSource } from 'typeorm';
 import { JsonSchemaService } from '../json-schema.service';
 
@@ -66,9 +70,7 @@ export class SchemaMigrationService {
       ]);
 
       if (!entities || entities.length === 0) {
-        throw new BadRequestException(
-          `Entity ${entityType} with ID ${entityId} not found.`
-        );
+        throw new NotFoundException(entityType, String(entityId));
       }
 
       const entity = entities[0];
@@ -125,8 +127,10 @@ export class SchemaMigrationService {
       );
 
       if (!validation.isValid) {
-        throw new BadRequestException(
-          `Migration failed: Resulting data does not match target schema v${targetSchema.version}. Errors: ${JSON.stringify(validation.errors)}`
+        throw new BusinessException(
+          'SCHEMA_MIGRATION_VALIDATION_FAILED',
+          `Migration failed: Data does not match target schema v${targetSchema.version}`,
+          'การ Migration ล้มเหลว: ข้อมูลไม่ตรงกับ Schema เป้าหมาย'
         );
       }
 

backend/src/modules/json-schema/services/ui-schema.service.ts

@@ -1,5 +1,6 @@
 // File: src/modules/json-schema/services/ui-schema.service.ts
-import { Injectable, BadRequestException, Logger } from '@nestjs/common';
+import { Injectable, Logger } from '@nestjs/common';
+import { ValidationException } from '../../../common/exceptions';
 import {
   UiSchema,
   UiSchemaField,
@@ -21,8 +22,8 @@ export class UiSchemaService {
 
     // 1. Validate Structure เบื้องต้น
     if (!uiSchema.layout || !uiSchema.fields) {
-      throw new BadRequestException(
-        'UI Schema must contain "layout" and "fields" properties.'
+      throw new ValidationException(
+        'UI Schema must contain "layout" and "fields" properties'
       );
     }
 
@@ -34,7 +35,7 @@ export class UiSchemaService {
       group.fields.forEach((fieldKey) => {
         layoutFields.add(fieldKey);
         if (!definedFields.has(fieldKey)) {
-          throw new BadRequestException(
+          throw new ValidationException(
             `Field "${fieldKey}" used in layout "${group.title}" is not defined in "fields".`
           );
         }

backend/src/modules/migration/migration.service.ts

@@ -1,10 +1,11 @@
+import { Injectable, Logger } from '@nestjs/common';
 import {
-  Injectable,
-  Logger,
+  BusinessException,
   ConflictException,
-  BadRequestException,
-  InternalServerErrorException,
-} from '@nestjs/common';
+  NotFoundException,
+  SystemException,
+  ValidationException,
+} from '../../common/exceptions';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository, DataSource } from 'typeorm';
 import { ImportCorrespondenceDto } from './dto/import-correspondence.dto';
@@ -57,7 +58,7 @@ export class MigrationService {
     userId: number
   ) {
     if (!idempotencyKey) {
-      throw new BadRequestException('Idempotency-Key header is required');
+      throw new ValidationException('Idempotency-Key header is required');
     }
 
     // 1. Idempotency Check
@@ -76,7 +77,10 @@ export class MigrationService {
         };
       } else {
         throw new ConflictException(
-          `Transaction failed previously with status ${existingTransaction.statusCode}`
+          'MIGRATION_DUPLICATE_TRANSACTION',
+          `Transaction failed previously with status ${existingTransaction.statusCode}`,
+          'รายการนี้เคยดำเนินการไปแล้วและล้มเหลว',
+          ['ตรวจสอบสถานะ Transaction ก่อนหน้า', 'ลองใช้ Idempotency-Key ใหม่']
         );
       }
     }
@@ -114,8 +118,8 @@ export class MigrationService {
     }
 
     if (!typeId) {
-      throw new BadRequestException(
-        `Category "${dto.category}" not found in system.`
+      throw new ValidationException(
+        `Category "${dto.category}" not found in system`
       );
     }
 
@@ -129,8 +133,8 @@ export class MigrationService {
       });
     }
     if (!status) {
-      throw new InternalServerErrorException(
-        'CRITICAL: No default correspondence status found (missing CLBOWN/DRAFT)'
+      throw new SystemException(
+        'No default correspondence status found (missing CLBOWN/DRAFT)'
       );
     }
 
@@ -139,9 +143,7 @@ export class MigrationService {
       where: { id: dto.projectId },
     });
     if (!project) {
-      throw new BadRequestException(
-        `Project ID ${dto.projectId} not found in database`
-      );
+      throw new NotFoundException('Project', String(dto.projectId));
     }
 
     const isRFA = type?.typeCode === 'RFA' || dto.category === 'RFA';
@@ -397,9 +399,7 @@ export class MigrationService {
       });
       await this.importTransactionRepo.save(failedTransaction).catch(() => {});
 
-      throw new InternalServerErrorException(
-        'Migration import failed: ' + errorMessage
-      );
+      throw new SystemException('Migration import failed: ' + errorMessage);
     } finally {
       await queryRunner.release();
     }
@@ -407,7 +407,7 @@ export class MigrationService {
 
   async enqueueRecord(dto: EnqueueMigrationDto) {
     if (!dto.documentNumber) {
-      throw new BadRequestException('documentNumber is required');
+      throw new ValidationException('documentNumber is required');
     }
 
     // Determine status based on confidence policy in ADR-017
@@ -492,7 +492,7 @@ export class MigrationService {
   async getQueueItemById(id: number) {
     const item = await this.reviewQueueRepo.findOne({ where: { id } });
     if (!item) {
-      throw new BadRequestException(`Queue item with ID ${id} not found`);
+      throw new NotFoundException('Queue item', String(id));
     }
     return item;
   }
@@ -538,12 +538,14 @@ export class MigrationService {
   ) {
     const queueItem = await this.reviewQueueRepo.findOne({ where: { id } });
     if (!queueItem) {
-      throw new BadRequestException(`Queue item ${id} not found`);
+      throw new NotFoundException('Queue item', String(id));
     }
 
     if (queueItem.status !== MigrationReviewStatus.PENDING) {
-      throw new BadRequestException(
-        `Queue item ${id} is already ${queueItem.status}`
+      throw new BusinessException(
+        'MIGRATION_ITEM_NOT_PENDING',
+        `Queue item ${id} is already ${queueItem.status}`,
+        'รายการนี้ไม่อยู่ในสถานะ PENDING'
       );
     }
 
@@ -565,7 +567,7 @@ export class MigrationService {
     userId: number
   ) {
     if (!idempotencyKey) {
-      throw new BadRequestException('Idempotency-Key header is required');
+      throw new ValidationException('Idempotency-Key header is required');
     }
 
     const results = [];
@@ -612,7 +614,7 @@ export class MigrationService {
   async rejectQueueItem(id: number, userId: number) {
     const queueItem = await this.reviewQueueRepo.findOne({ where: { id } });
     if (!queueItem) {
-      throw new BadRequestException('Queue item not found');
+      throw new NotFoundException('Queue item', String(id));
     }
 
     queueItem.status = MigrationReviewStatus.REJECTED;
@@ -628,12 +630,12 @@ export class MigrationService {
 
   getStagingFileStream(filePath: string) {
     if (!filePath) {
-      throw new BadRequestException('File path is required');
+      throw new ValidationException('File path is required');
     }
 
     const resolvedPath = path.resolve(filePath);
     if (!existsSync(resolvedPath)) {
-      throw new BadRequestException('File not found at specified path');
+      throw new NotFoundException('File', filePath);
     }
 
     return createReadStream(resolvedPath);

backend/src/modules/rfa/rfa.service.ts

@@ -1,13 +1,14 @@
 // File: src/modules/rfa/rfa.service.ts
 
+import { Injectable, Logger } from '@nestjs/common';
 import {
-  BadRequestException,
-  ForbiddenException,
-  Injectable,
-  InternalServerErrorException,
-  Logger,
+  BusinessException,
   NotFoundException,
-} from '@nestjs/common';
+  PermissionException,
+  SystemException,
+  ValidationException,
+  WorkflowException,
+} from '../../common/exceptions';
 import { InjectRepository } from '@nestjs/typeorm';
 import { DataSource, In, Repository } from 'typeorm';
 
@@ -122,7 +123,8 @@ export class RfaService {
     const rfaType = await this.rfaTypeRepo.findOne({
       where: { id: createDto.rfaTypeId },
     });
-    if (!rfaType) throw new NotFoundException('RFA Type not found');
+    if (!rfaType)
+      throw new NotFoundException('RFA Type', String(createDto.rfaTypeId));
 
     const rfaTypeCode = rfaType.typeCode.toUpperCase();
     const rawShopDrawingRefs = createDto.shopDrawingRevisionIds ?? [];
@@ -130,25 +132,25 @@ export class RfaService {
 
     if (['DDW', 'SDW'].includes(rfaTypeCode)) {
       if (rawShopDrawingRefs.length === 0) {
-        throw new BadRequestException(
+        throw new ValidationException(
           'Selected RFA Type requires at least one Shop Drawing Revision'
         );
       }
 
       if (rawAsBuiltDrawingRefs.length > 0) {
-        throw new BadRequestException(
+        throw new ValidationException(
           'Selected RFA Type cannot reference As-Built Drawing Revisions'
         );
       }
     } else if (rfaTypeCode === 'ADW') {
       if (rawAsBuiltDrawingRefs.length === 0) {
-        throw new BadRequestException(
+        throw new ValidationException(
           'Selected RFA Type requires at least one As-Built Drawing Revision'
         );
       }
 
       if (rawShopDrawingRefs.length > 0) {
-        throw new BadRequestException(
+        throw new ValidationException(
           'Selected RFA Type cannot reference Shop Drawing Revisions'
         );
       }
@@ -156,7 +158,7 @@ export class RfaService {
       rawShopDrawingRefs.length > 0 ||
       rawAsBuiltDrawingRefs.length > 0
     ) {
-      throw new BadRequestException(
+      throw new ValidationException(
         'Selected RFA Type does not support drawing revision items'
       );
     }
@@ -185,7 +187,7 @@ export class RfaService {
       where: { typeCode: 'RFA', isActive: true },
     });
     if (!correspondenceType) {
-      throw new InternalServerErrorException(
+      throw new SystemException(
         'Correspondence Type RFA not found in Master Data'
       );
     }
@@ -195,8 +197,11 @@ export class RfaService {
       : rfaType.contractId;
 
     if (rfaType.contractId !== internalContractId) {
-      throw new BadRequestException(
-        'Selected RFA Type does not belong to the selected contract'
+      throw new BusinessException(
+        'RFA_TYPE_CONTRACT_MISMATCH',
+        'Selected RFA Type does not belong to the selected contract',
+        'ประเภท RFA ที่เลือกไม่ตรงกับสัญญาที่ระบุ',
+        ['เลือกประเภท RFA ที่ตรงกับสัญญา']
       );
     }
 
@@ -206,12 +211,18 @@ export class RfaService {
       });
 
       if (!discipline) {
-        throw new NotFoundException('Discipline not found');
+        throw new NotFoundException(
+          'Discipline',
+          String(createDto.disciplineId)
+        );
       }
 
       if (discipline.contractId !== internalContractId) {
-        throw new BadRequestException(
-          'Selected Discipline does not belong to the selected contract'
+        throw new BusinessException(
+          'DISCIPLINE_CONTRACT_MISMATCH',
+          'Selected Discipline does not belong to the selected contract',
+          'Discipline ที่เลือกไม่ตรงกับสัญญาที่ระบุ',
+          ['เลือก Discipline ที่ตรงกับสัญญา']
         );
       }
     }
@@ -226,9 +237,7 @@ export class RfaService {
       where: { statusCode: 'DFT' },
     });
     if (!statusDraft) {
-      throw new InternalServerErrorException(
-        'Status DFT (Draft) not found in Master Data'
-      );
+      throw new SystemException('Status DFT (Draft) not found in Master Data');
     }
 
     const resolvedOriginatorId = createDto.originatorId
@@ -247,15 +256,18 @@ export class RfaService {
         user.user_id
       );
       if (!canManageAll) {
-        throw new ForbiddenException(
-          'You do not have permission to create documents on behalf of other organizations.'
+        throw new PermissionException(
+          'rfa',
+          'create on behalf of other organization'
         );
       }
       userOrgId = resolvedOriginatorId;
     }
 
     if (!userOrgId) {
-      throw new BadRequestException('User must belong to an organization');
+      throw new ValidationException(
+        'User must belong to an organization to create RFA'
+      );
     }
 
     // EC-RFA-001: Check for existing active RFA per Shop Drawing Revision
@@ -273,9 +285,11 @@ export class RfaService {
         .getMany();
 
       if (conflictingItems.length > 0) {
-        throw new BadRequestException(
-          '[EC-RFA-001] One or more selected Shop Drawing Revisions already have an active RFA. ' +
-            'A Shop Drawing Revision can only be referenced by one active RFA at a time.'
+        throw new BusinessException(
+          'EC_RFA_001_ACTIVE_RFA_EXISTS',
+          '[EC-RFA-001] One or more selected Shop Drawing Revisions already have an active RFA.',
+          'Shop Drawing Revision ที่เลือกมี RFA ที่ยังใช้งานอยู่แล้ว',
+          ['ตรวจสอบ RFA ที่มีอยู่', 'เลือก Shop Drawing Revision อื่น']
         );
       }
     }
@@ -315,8 +329,8 @@ export class RfaService {
         }
       );
       if (!corrStatusDraft)
-        throw new InternalServerErrorException(
-          'Correspondence Status DRAFT not found'
+        throw new SystemException(
+          'Correspondence Status DRAFT not found in Master Data'
         );
 
       // 1. Create Correspondence Record
@@ -385,7 +399,7 @@ export class RfaService {
         });
 
         if (shopDrawings.length !== shopDrawingRevisionIds.length) {
-          throw new NotFoundException('Some Shop Drawing Revisions not found');
+          throw new NotFoundException('Shop Drawing Revision');
         }
 
         rfaItems.push(
@@ -405,9 +419,7 @@ export class RfaService {
         });
 
         if (asBuiltDrawings.length !== asBuiltDrawingRevisionIds.length) {
-          throw new NotFoundException(
-            'Some As-Built Drawing Revisions not found'
-          );
+          throw new NotFoundException('As-Built Drawing Revision');
         }
 
         rfaItems.push(
@@ -588,7 +600,7 @@ export class RfaService {
       select: ['id'],
     });
     if (!correspondence) {
-      throw new NotFoundException(`RFA with publicId ${publicId} not found`);
+      throw new NotFoundException('RFA', publicId);
     }
     return this.findOne(correspondence.id);
   }
@@ -599,7 +611,7 @@ export class RfaService {
       select: ['id'],
     });
     if (!correspondence) {
-      throw new NotFoundException(`RFA with publicId ${publicId} not found`);
+      throw new NotFoundException('RFA', publicId);
     }
     return this.findOne(correspondence.id, true);
   }
@@ -628,7 +640,7 @@ export class RfaService {
     });
 
     if (!rfa) {
-      throw new NotFoundException(`RFA ID ${id} not found`);
+      throw new NotFoundException('RFA', String(id));
     }
 
     if (rawEntities) {
@@ -657,12 +669,17 @@ export class RfaService {
       (rfa.correspondence?.revisions as CorrRevWithRfa[] | undefined) ?? [];
     const currentCorrRev = corrRevisions.find((r) => r.isCurrent);
     if (!currentCorrRev || !currentCorrRev.rfaRevision)
-      throw new NotFoundException('Current revision not found');
+      throw new NotFoundException('Current revision');
 
     const currentRfaRev = currentCorrRev.rfaRevision;
 
     if (currentRfaRev.statusCode.statusCode !== 'DFT') {
-      throw new BadRequestException('Only DRAFT documents can be submitted');
+      throw new WorkflowException(
+        'RFA_INVALID_SUBMIT_STATUS',
+        'Only DRAFT documents can be submitted',
+        'สามารถส่งได้เฉพาะเอกสารสถานะ DRAFT เท่านั้น',
+        ['ตรวจสอบสถานะเอกสารปัจจุบัน']
+      );
     }
 
     const template = await this.templateRepo.findOne({
@@ -671,7 +688,12 @@ export class RfaService {
     });
 
     if (!template) {
-      throw new BadRequestException('Invalid routing template');
+      throw new BusinessException(
+        'ROUTING_TEMPLATE_NOT_FOUND',
+        'Invalid routing template',
+        'ไม่พบ Routing Template ที่กำหนด',
+        ['ตรวจสอบ Routing Template ที่ตั้งค่าไว้']
+      );
     }
 
     // Manual fetch of steps
@@ -681,14 +703,19 @@ export class RfaService {
     });
 
     if (steps.length === 0) {
-      throw new BadRequestException('Routing template has no steps');
+      throw new BusinessException(
+        'ROUTING_TEMPLATE_EMPTY',
+        'Routing template has no steps',
+        'Routing Template ไม่มีขั้นตอนกำหนดไว้',
+        ['เพิ่ม Step ใน Routing Template']
+      );
     }
 
     const statusForApprove = await this.rfaStatusRepo.findOne({
       where: { statusCode: 'FAP' },
     });
     if (!statusForApprove)
-      throw new InternalServerErrorException('Status FAP not found');
+      throw new SystemException('Status FAP not found in Master Data');
 
     const queryRunner = this.dataSource.createQueryRunner();
     await queryRunner.connect();
@@ -765,11 +792,14 @@ export class RfaService {
     });
 
     if (!currentRouting)
-      throw new BadRequestException('No active workflow step found');
-    if (currentRouting.toOrganizationId !== user.primaryOrganizationId) {
-      throw new ForbiddenException(
-        'You are not authorized to process this step'
+      throw new WorkflowException(
+        'NO_ACTIVE_WORKFLOW_STEP',
+        'No active workflow step found',
+        'ไม่พบขั้นตอน Workflow ที่ยังเปิดอยู่',
+        ['ตรวจสอบสถานะ Workflow ของเอกสาร']
       );
+    if (currentRouting.toOrganizationId !== user.primaryOrganizationId) {
+      throw new PermissionException('rfa workflow step', 'process');
     }
 
     const template = await this.templateRepo.findOne({
@@ -777,7 +807,10 @@ export class RfaService {
       // relations: ['steps'],
     });
 
-    if (!template) throw new InternalServerErrorException('Template not found');
+    if (!template)
+      throw new SystemException(
+        'Routing Template not found for workflow processing'
+      );
 
     // Manual fetch steps
     const steps = await this.templateStepRepo.find({
@@ -786,7 +819,7 @@ export class RfaService {
     });
 
     if (steps.length === 0)
-      throw new InternalServerErrorException('Template steps not found');
+      throw new SystemException('Routing Template steps not found');
 
     // Call Engine to calculate next step
     const result = this.workflowEngine.processAction(
@@ -874,13 +907,16 @@ export class RfaService {
       (rfa.correspondence?.revisions as CorrRevWithRfa[] | undefined) ?? [];
     const currentCorrRev = corrRevisions.find((r) => r.isCurrent);
     if (!currentCorrRev || !currentCorrRev.rfaRevision)
-      throw new NotFoundException('Current revision not found');
+      throw new NotFoundException('Current revision');
 
     const currentRfaRev = currentCorrRev.rfaRevision;
 
     if (currentRfaRev.statusCode.statusCode !== 'DFT') {
-      throw new BadRequestException(
-        'Only DRAFT documents can be edited. Submit a new revision for non-draft documents.'
+      throw new WorkflowException(
+        'RFA_EDIT_NON_DRAFT',
+        'Only DRAFT documents can be edited',
+        'สามารถแก้ไขได้เฉพาะเอกสารสถานะ DRAFT เท่านั้น',
+        ['ส่งเอกสารเพื่อสร้าง Revision ใหม่สำหรับเอกสารที่ไม่ใช่ DRAFT']
       );
     }
 
@@ -915,13 +951,16 @@ export class RfaService {
       (rfa.correspondence?.revisions as CorrRevWithRfa[] | undefined) ?? [];
     const currentCorrRev = corrRevisions.find((r) => r.isCurrent);
     if (!currentCorrRev || !currentCorrRev.rfaRevision)
-      throw new NotFoundException('Current revision not found');
+      throw new NotFoundException('Current revision');
 
     const currentRfaRev = currentCorrRev.rfaRevision;
 
     if (currentRfaRev.statusCode.statusCode !== 'DFT') {
-      throw new BadRequestException(
-        'Only DRAFT documents can be cancelled. Contact an Org Admin to cancel submitted documents.'
+      throw new WorkflowException(
+        'RFA_CANCEL_NON_DRAFT',
+        'Only DRAFT documents can be cancelled',
+        'สามารถยกเลิกได้เฉพาะเอกสารสถานะ DRAFT เท่านั้น',
+        ['ติดต่อ Org Admin เพื่อยกเลิกเอกสารที่ส่งแล้ว']
       );
     }
 
@@ -929,7 +968,7 @@ export class RfaService {
       where: { statusCode: 'CC' },
     });
     if (!statusCC)
-      throw new InternalServerErrorException(
+      throw new SystemException(
         'Status CC (Cancelled) not found in Master Data'
       );
 

backend/src/modules/transmittal/transmittal.service.ts

@@ -1,11 +1,10 @@
+import { Injectable, Logger } from '@nestjs/common';
 import {
-  Injectable,
-  Logger,
   NotFoundException,
-  InternalServerErrorException,
-  BadRequestException,
-  ForbiddenException,
-} from '@nestjs/common';
+  PermissionException,
+  SystemException,
+  ValidationException,
+} from '../../common/exceptions';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository, DataSource } from 'typeorm';
 import { Transmittal } from './entities/transmittal.entity';
@@ -57,13 +56,13 @@ export class TransmittalService {
     const type = await this.typeRepo.findOne({
       where: { typeCode: 'TRN' }, // Adjust code as per Master Data
     });
-    if (!type) throw new NotFoundException('Transmittal Type (TRN) not found');
+    if (!type) throw new NotFoundException('Transmittal Type (TRN)');
 
     const statusDraft = await this.statusRepo.findOne({
       where: { statusCode: 'DRAFT' },
     });
     if (!statusDraft)
-      throw new InternalServerErrorException('Status DRAFT not found');
+      throw new SystemException('Status DRAFT not found in Master Data');
 
     const queryRunner = this.dataSource.createQueryRunner();
     await queryRunner.connect();
@@ -86,15 +85,16 @@ export class TransmittalService {
         user.user_id
       );
       if (!canManageAll) {
-        throw new ForbiddenException(
-          'You do not have permission to create documents on behalf of other organizations.'
+        throw new PermissionException(
+          'transmittal',
+          'create on behalf of other organization'
         );
       }
       userOrgId = resolvedOriginatorId;
     }
 
     if (!userOrgId) {
-      throw new BadRequestException(
+      throw new ValidationException(
         'User must belong to an organization to create a transmittal'
       );
     }

backend/src/modules/user/user-assignment.service.ts

@@ -1,4 +1,5 @@
-import { Injectable, BadRequestException, Logger } from '@nestjs/common';
+import { Injectable, Logger } from '@nestjs/common';
+import { ValidationException } from '../../common/exceptions';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository, DataSource } from 'typeorm';
 import { UserAssignment } from './entities/user-assignment.entity';
@@ -22,7 +23,7 @@ export class UserAssignmentService {
       (v) => v != null
     );
     if (scopes.length > 1) {
-      throw new BadRequestException(
+      throw new ValidationException(
         'Cannot assign multiple scopes at once. Choose one of Org, Project, or Contract.'
       );
     }
@@ -55,7 +56,7 @@ export class UserAssignmentService {
           // Validation (Scope)
           const scopes = [organizationId, projectId].filter((v) => v != null);
           if (scopes.length > 1) {
-            throw new BadRequestException(
+            throw new ValidationException(
               `User ${userId}: Cannot assign multiple scopes.`
             );
           }

backend/src/modules/user/user.service.ts

@@ -1,12 +1,8 @@
 // File: src/modules/user/user.service.ts
 // บันทึกการแก้ไข: แก้ไข Error TS1272 โดยใช้ 'import type' สำหรับ Cache interface (T1.3)
 
-import {
-  Injectable,
-  NotFoundException,
-  ConflictException,
-  Inject,
-} from '@nestjs/common';
+import { Injectable, Inject } from '@nestjs/common';
+import { NotFoundException, ConflictException } from '../../common/exceptions';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
 import { CACHE_MANAGER } from '@nestjs/cache-manager';
@@ -56,7 +52,12 @@ export class UserService {
     } catch (error: unknown) {
       const dbError = error as { code?: string };
       if (dbError.code === 'ER_DUP_ENTRY') {
-        throw new ConflictException('Username or Email already exists');
+        throw new ConflictException(
+          'USER_DUPLICATE',
+          'Username or Email already exists',
+          'ชื่อผู้ใช้หรืออีเมลนี้มีอยู่ในระบบแล้ว',
+          ['ลองใช้ชื่อผู้ใช้หรืออีเมลอื่น']
+        );
       }
       throw error;
     }
@@ -152,7 +153,7 @@ export class UserService {
     });
 
     if (!user) {
-      throw new NotFoundException(`User with ID ${id} not found`);
+      throw new NotFoundException('User', String(id));
     }
 
     return user;
@@ -171,7 +172,7 @@ export class UserService {
     });
 
     if (!user) {
-      throw new NotFoundException(`User with publicId ${publicId} not found`);
+      throw new NotFoundException('User', publicId);
     }
 
     return user;
@@ -217,7 +218,7 @@ export class UserService {
     const result = await this.usersRepository.softDelete(user.user_id);
 
     if (result.affected === 0) {
-      throw new NotFoundException(`User with UUID ${uuid} not found`);
+      throw new NotFoundException('User', uuid);
     }
     // เคลียร์ Cache เมื่อลบ
     await this.clearUserCache(user.user_id);
@@ -275,7 +276,7 @@ export class UserService {
     });
 
     if (!role) {
-      throw new NotFoundException(`Role ID ${roleId} not found`);
+      throw new NotFoundException('Role', String(roleId));
     }
 
     // Load permissions entities

backend/src/modules/workflow-engine/dsl/parser.service.ts

@@ -1,4 +1,9 @@
-import { Injectable, Logger, BadRequestException } from '@nestjs/common';
+import { Injectable, Logger } from '@nestjs/common';
+import {
+  NotFoundException,
+  ValidationException,
+  WorkflowException,
+} from '../../../common/exceptions';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
 import { WorkflowDslSchema, WorkflowDsl } from './workflow-dsl.schema';
@@ -36,16 +41,18 @@ export class WorkflowDslParser {
       return await this.workflowDefRepo.save(definition);
     } catch (error: unknown) {
       if (error instanceof SyntaxError) {
-        throw new BadRequestException(`Invalid JSON: ${error.message}`);
+        throw new ValidationException(`Invalid JSON: ${error.message}`);
       }
       const err = error as {
         name?: string;
-        errors?: unknown;
+        errors?: unknown[];
         message?: string;
       };
       if (err.name === 'ZodError') {
-        throw new BadRequestException(
-          `Invalid workflow DSL: ${JSON.stringify(err.errors)}`
+        throw new WorkflowException(
+          'INVALID_WORKFLOW_DSL',
+          `Invalid workflow DSL: ${JSON.stringify(err.errors)}`,
+          'Workflow DSL ไม่ถูกต้อง'
         );
       }
       throw error;
@@ -66,16 +73,20 @@ export class WorkflowDslParser {
 
     // 1. Validate initial state
     if (!stateSet.has(dsl.initialState)) {
-      throw new BadRequestException(
-        `Initial state "${dsl.initialState}" not found in states array`
+      throw new WorkflowException(
+        'DSL_INVALID_INITIAL_STATE',
+        `Initial state "${dsl.initialState}" not found in states array`,
+        'Initial State ไม่พบใน States Array'
       );
     }
 
     // 2. Validate final states
     dsl.finalStates.forEach((state) => {
       if (!stateSet.has(state)) {
-        throw new BadRequestException(
-          `Final state "${state}" not found in states array`
+        throw new WorkflowException(
+          'DSL_INVALID_FINAL_STATE',
+          `Final state "${state}" not found in states array`,
+          'Final State ไม่พบใน States Array'
         );
       }
     });
@@ -86,15 +97,19 @@ export class WorkflowDslParser {
     dsl.transitions.forEach((transition, index) => {
       // Check 'from' state
       if (!stateSet.has(transition.from)) {
-        throw new BadRequestException(
-          `Transition ${index}: 'from' state "${transition.from}" not found in states array`
+        throw new WorkflowException(
+          'DSL_INVALID_TRANSITION_FROM',
+          `Transition ${index}: 'from' state "${transition.from}" not found in states array`,
+          'Transition อ้างอิง State ที่ไม่พบ'
         );
       }
 
       // Check 'to' state
       if (!stateSet.has(transition.to)) {
-        throw new BadRequestException(
-          `Transition ${index}: 'to' state "${transition.to}" not found in states array`
+        throw new WorkflowException(
+          'DSL_INVALID_TRANSITION_TO',
+          `Transition ${index}: 'to' state "${transition.to}" not found in states array`,
+          'Transition อ้างอิง State ที่ไม่พบ'
         );
       }
 
@@ -120,8 +135,10 @@ export class WorkflowDslParser {
     dsl.transitions.forEach((transition) => {
       const key = `${transition.from}-${transition.trigger}-${transition.to}`;
       if (transitionKeys.has(key)) {
-        throw new BadRequestException(
-          `Duplicate transition: ${transition.from} --[${transition.trigger}]--> ${transition.to}`
+        throw new WorkflowException(
+          'DSL_DUPLICATE_TRANSITION',
+          `Duplicate transition: ${transition.from} --[${transition.trigger}]--> ${transition.to}`,
+          'DSL มี Transition ซ้ำซ้อน'
         );
       }
       transitionKeys.add(key);
@@ -158,9 +175,7 @@ export class WorkflowDslParser {
     });
 
     if (!definition) {
-      throw new BadRequestException(
-        `Workflow definition ${definitionId} not found`
-      );
+      throw new NotFoundException('Workflow definition', String(definitionId));
     }
 
     try {
@@ -171,8 +186,10 @@ export class WorkflowDslParser {
         `Failed to parse stored DSL for definition ${definitionId}`,
         error
       );
-      throw new BadRequestException(
-        `Invalid stored DSL: ${error instanceof Error ? error.message : String(error)}`
+      throw new WorkflowException(
+        'INVALID_STORED_DSL',
+        `Invalid stored DSL: ${error instanceof Error ? error.message : String(error)}`,
+        'DSL ที่บันทึกไว้ไม่ถูกต้อง'
       );
     }
   }

backend/src/modules/workflow-engine/workflow-dsl.service.ts

@@ -1,6 +1,10 @@
 // File: src/modules/workflow-engine/workflow-dsl.service.ts
 
-import { BadRequestException, Injectable, Logger } from '@nestjs/common';
+import { Injectable, Logger } from '@nestjs/common';
+import {
+  ValidationException,
+  WorkflowException,
+} from '../../common/exceptions';
 
 // ==========================================
 // 1. Interfaces for RAW DSL (Input from User)
@@ -86,8 +90,11 @@ export class WorkflowDslService {
     for (const rawState of dsl.states) {
       if (rawState.initial) {
         if (initialFound) {
-          throw new BadRequestException(
-            `DSL Error: Multiple initial states found (at "${rawState.name}").`
+          throw new WorkflowException(
+            'DSL_MULTIPLE_INITIAL_STATES',
+            `DSL Error: Multiple initial states found (at "${rawState.name}")`,
+            'DSL มี Initial State หลายค่า แต่ละ Workflow ต้องมีเพียง Initial State เดียว',
+            ['ตรวจสอบโครงสร้าง DSL และแก้ไข Initial State']
           );
         }
         compiled.initialState = rawState.name;
@@ -104,8 +111,11 @@ export class WorkflowDslService {
         for (const [action, rule] of Object.entries(rawState.on)) {
           // Validation: Target state must exist
           if (!definedStates.has(rule.to)) {
-            throw new BadRequestException(
-              `DSL Error: State "${rawState.name}" transitions via "${action}" to unknown state "${rule.to}".`
+            throw new WorkflowException(
+              'DSL_UNKNOWN_TRANSITION_TARGET',
+              `DSL Error: State "${rawState.name}" transitions via "${action}" to unknown state "${rule.to}"`,
+              'DSL อ้างอิง State ที่ไม่พบ',
+              ['ตรวจสอบชื่อ State ที่กำหนดใน Transition']
             );
           }
 
@@ -133,7 +143,12 @@ export class WorkflowDslService {
     }
 
     if (!initialFound) {
-      throw new BadRequestException('DSL Error: No initial state defined.');
+      throw new WorkflowException(
+        'DSL_NO_INITIAL_STATE',
+        'DSL Error: No initial state defined',
+        'DSL ไม่มีการกำหนด Initial State',
+        ['เพิ่ม initial: true ใน State หนึ่ง']
+      );
     }
 
     return compiled;
@@ -153,15 +168,21 @@ export class WorkflowDslService {
 
     // 1. Validate State Existence
     if (!stateConfig) {
-      throw new BadRequestException(
-        `Runtime Error: Current state "${currentState}" is invalid.`
+      throw new WorkflowException(
+        'WORKFLOW_INVALID_CURRENT_STATE',
+        `Runtime Error: Current state "${currentState}" is invalid`,
+        'Workflow อยู่ในสถานะที่ไม่รู้จัก',
+        ['ตรวจสอบ DSL ของ Workflow']
       );
     }
 
     // 2. Check if terminal
     if (stateConfig.terminal) {
-      throw new BadRequestException(
-        `Runtime Error: Cannot transition from terminal state "${currentState}".`
+      throw new WorkflowException(
+        'WORKFLOW_TERMINAL_STATE',
+        `Runtime Error: Cannot transition from terminal state "${currentState}"`,
+        'ไม่สามารถดำเนินการจาก State สุดท้ายได้',
+        ['เอกสารสิ้นสุดกระบวนการแล้ว']
       );
     }
 
@@ -169,8 +190,11 @@ export class WorkflowDslService {
     const transition = stateConfig.transitions[action];
     if (!transition) {
       const allowed = Object.keys(stateConfig.transitions).join(', ');
-      throw new BadRequestException(
-        `Invalid Action: "${action}" is not allowed from "${currentState}". Allowed: [${allowed}]`
+      throw new WorkflowException(
+        'WORKFLOW_INVALID_ACTION',
+        `Invalid Action: "${action}" is not allowed from "${currentState}". Allowed: [${allowed}]`,
+        `ไม่สามารถดำเนินการ "${action}" ในสถานะปัจจุบัน ทำได้: [${allowed}]`,
+        ['เลือกการดำเนินการที่อนุญาตจากรายการ']
       );
     }
 
@@ -181,8 +205,11 @@ export class WorkflowDslService {
     if (transition.condition) {
       const isMet = this.evaluateCondition(transition.condition, context);
       if (!isMet) {
-        throw new BadRequestException(
-          'Condition Failed: The criteria for this transition are not met.'
+        throw new WorkflowException(
+          'WORKFLOW_CONDITION_NOT_MET',
+          'Condition Failed: The criteria for this transition are not met',
+          'เงื่อนไขสำหรับการดำเนินการนี้ไม่ผ่าน',
+          ['ตรวจสอบเงื่อนไขที่กำหนดใน Workflow']
         );
       }
     }
@@ -199,12 +226,12 @@ export class WorkflowDslService {
 
   private validateSchemaStructure(dsl: unknown) {
     if (!dsl || typeof dsl !== 'object') {
-      throw new BadRequestException('DSL must be a JSON object.');
+      throw new ValidationException('DSL must be a JSON object');
     }
     const d = dsl as Record<string, unknown>;
     if (!d.workflow || !d.states || !Array.isArray(d.states)) {
-      throw new BadRequestException(
-        'DSL Error: Missing required fields (workflow, states).'
+      throw new ValidationException(
+        'DSL Error: Missing required fields (workflow, states)'
       );
     }
   }
@@ -226,15 +253,23 @@ export class WorkflowDslService {
     if (requiredRoles.length > 0) {
       const hasRole = requiredRoles.some((r) => userRoles.includes(r));
       if (!hasRole) {
-        throw new BadRequestException(
-          `Access Denied: Required roles [${requiredRoles.join(', ')}]`
+        throw new WorkflowException(
+          'WORKFLOW_ROLE_REQUIRED',
+          `Access Denied: Required roles [${requiredRoles.join(', ')}]`,
+          `ต้องมี Role: [${requiredRoles.join(', ')}] จึงจะดำเนินการนี้ได้`,
+          ['ติดต่อผู้ดูแลระบบเพื่อขอสิทธิ์']
         );
       }
     }
 
     // Check Specific User
     if (req.userId && String(req.userId) !== String(userId)) {
-      throw new BadRequestException('Access Denied: User mismatch.');
+      throw new WorkflowException(
+        'WORKFLOW_USER_MISMATCH',
+        'Access Denied: User mismatch',
+        'ผู้ใช้ไม่ได้รับอนุญาตให้ดำเนินการนี้',
+        ['ตรวจสอบว่าเล็็กชื่ออีเมลที่ป้อนให้เข้าสู่ระบบ']
+      );
     }
   }
 

backend/src/modules/workflow-engine/workflow-engine.service.ts

@@ -1,14 +1,9 @@
 // File: src/modules/workflow-engine/workflow-engine.service.ts
 
-import {
-  BadRequestException,
-  Injectable,
-  Logger,
-  NotFoundException,
-} from '@nestjs/common';
+import { Injectable, Logger } from '@nestjs/common';
+import { NotFoundException, WorkflowException } from '../../common/exceptions';
 import { InjectRepository } from '@nestjs/typeorm';
 import { DataSource, Repository } from 'typeorm';
-
 // Entities
 import { WorkflowDefinition } from './entities/workflow-definition.entity';
 import { WorkflowHistory } from './entities/workflow-history.entity';
@@ -104,9 +99,7 @@ export class WorkflowEngineService {
   ): Promise<WorkflowDefinition> {
     const definition = await this.workflowDefRepo.findOne({ where: { id } });
     if (!definition) {
-      throw new NotFoundException(
-        `Workflow Definition with ID "${id}" not found`
-      );
+      throw new NotFoundException('Workflow Definition', id);
     }
 
     if (dto.dsl) {
@@ -115,8 +108,11 @@ export class WorkflowEngineService {
         definition.dsl = dto.dsl as unknown as Record<string, unknown>;
         definition.compiled = compiled as unknown as Record<string, unknown>;
       } catch (error: unknown) {
-        throw new BadRequestException(
-          `Invalid DSL: ${error instanceof Error ? error.message : String(error)}`
+        throw new WorkflowException(
+          'INVALID_WORKFLOW_DSL',
+          `Invalid DSL: ${error instanceof Error ? error.message : String(error)}`,
+          'Workflow DSL ไม่ถูกต้อง กรุณาตรวจสอบโครงสร้าง',
+          ['ตรวจสอบ syntax ของ DSL', 'ดูตัวอย่าง DSL ที่ถูกต้อง']
         );
       }
     }
@@ -149,9 +145,7 @@ export class WorkflowEngineService {
   async getDefinitionById(id: string): Promise<WorkflowDefinition> {
     const definition = await this.workflowDefRepo.findOne({ where: { id } });
     if (!definition) {
-      throw new NotFoundException(
-        `Workflow Definition with ID "${id}" not found`
-      );
+      throw new NotFoundException('Workflow Definition', id);
     }
     return definition;
   }
@@ -197,9 +191,7 @@ export class WorkflowEngineService {
     });
 
     if (!definition) {
-      throw new NotFoundException(
-        `Workflow "${workflowCode}" not found or inactive.`
-      );
+      throw new NotFoundException('Workflow', workflowCode);
     }
 
     // 2. หา Initial State จาก Compiled Structure
@@ -209,8 +201,11 @@ export class WorkflowEngineService {
     const initialState = compiled.initialState;
 
     if (!initialState) {
-      throw new BadRequestException(
-        `Workflow "${workflowCode}" has no initial state defined.`
+      throw new WorkflowException(
+        'WORKFLOW_NO_INITIAL_STATE',
+        `Workflow "${workflowCode}" has no initial state defined`,
+        'Workflow ไม่มี Initial State ที่กำหนด',
+        ['ตรวจสอบ DSL ของ Workflow นี้']
       );
     }
 
@@ -242,9 +237,7 @@ export class WorkflowEngineService {
     });
 
     if (!instance) {
-      throw new NotFoundException(
-        `Workflow Instance "${instanceId}" not found`
-      );
+      throw new NotFoundException('Workflow Instance', instanceId);
     }
 
     return instance;
@@ -276,14 +269,15 @@ export class WorkflowEngineService {
       });
 
       if (!instance) {
-        throw new NotFoundException(
-          `Workflow Instance "${instanceId}" not found.`
-        );
+        throw new NotFoundException('Workflow Instance', instanceId);
       }
 
       if (instance.status !== WorkflowStatus.ACTIVE) {
-        throw new BadRequestException(
-          `Workflow is not active (Status: ${instance.status}).`
+        throw new WorkflowException(
+          'WORKFLOW_NOT_ACTIVE',
+          `Workflow is not active (Status: ${instance.status})`,
+          'Workflow ไม่อยู่ในสถานะ Active',
+          ['ตรวจสอบสถานะของ Workflow']
         );
       }
 
@@ -427,7 +421,12 @@ export class WorkflowEngineService {
       case 'RETURN': {
         const targetStep = returnToSequence || currentSequence - 1;
         if (targetStep < 1) {
-          throw new BadRequestException('Cannot return beyond the first step');
+          throw new WorkflowException(
+            'WORKFLOW_INVALID_RETURN_TARGET',
+            'Cannot return beyond the first step',
+            'ไม่สามารถส่งคืนไปเกินกว่าขั้นตอนแรกได้',
+            ['ตรวจสอบลำดับขั้นตอนที่ต้องการส่งคืน']
+          );
         }
         return {
           nextStepSequence: targetStep,