refactor use cases

core/identity/application/use-cases/GetCurrentSessionUseCase.ts

@@ -1,6 +1,23 @@
 import { User } from '../../domain/entities/User';
 import { IUserRepository } from '../../domain/repositories/IUserRepository';
-// No direct import of apps/api DTOs in core module
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+
+export type GetCurrentSessionInput = {
+  userId: string;
+};
+
+export type GetCurrentSessionResult = {
+  user: User;
+};
+
+export type GetCurrentSessionErrorCode = 'USER_NOT_FOUND' | 'REPOSITORY_ERROR';
+
+export type GetCurrentSessionApplicationError = ApplicationErrorCode<
+  GetCurrentSessionErrorCode,
+  { message: string }
+>;
 
 /**
  * Application Use Case: GetCurrentSessionUseCase
@@ -8,13 +25,45 @@ import { IUserRepository } from '../../domain/repositories/IUserRepository';
  * Retrieves the current user session information.
  */
 export class GetCurrentSessionUseCase {
-  constructor(private userRepo: IUserRepository) {}
+  constructor(
+    private readonly userRepo: IUserRepository,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<GetCurrentSessionResult>,
+  ) {}
 
-  async execute(userId: string): Promise<User | null> {
-    const stored = await this.userRepo.findById(userId);
-    if (!stored) {
-      return null;
+  async execute(input: GetCurrentSessionInput): Promise<
+    Result<void, GetCurrentSessionApplicationError>
+  > {
+    try {
+      const stored = await this.userRepo.findById(input.userId);
+      if (!stored) {
+        return Result.err({
+          code: 'USER_NOT_FOUND',
+          details: { message: 'User not found' },
+        } as GetCurrentSessionApplicationError);
+      }
+
+      const user = User.fromStored(stored);
+      const result: GetCurrentSessionResult = { user };
+      this.output.present(result);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message
+          ? error.message
+          : 'Failed to execute GetCurrentSessionUseCase';
+
+      this.logger.error(
+        'GetCurrentSessionUseCase.execute failed',
+        error instanceof Error ? error : undefined,
+        { input },
+      );
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as GetCurrentSessionApplicationError);
     }
-    return User.fromStored(stored);
   }
 }

core/identity/application/use-cases/GetCurrentUserSessionUseCase.ts

@@ -1,14 +1,50 @@
 import type { AuthSessionDTO } from '../dto/AuthSessionDTO';
 import type { IdentitySessionPort } from '../ports/IdentitySessionPort';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+
+export type GetCurrentUserSessionInput = void;
+
+export type GetCurrentUserSessionResult = AuthSessionDTO | null;
+
+export type GetCurrentUserSessionErrorCode = 'REPOSITORY_ERROR';
+
+export type GetCurrentUserSessionApplicationError = ApplicationErrorCode<
+  GetCurrentUserSessionErrorCode,
+  { message: string }
+>;
 
 export class GetCurrentUserSessionUseCase {
-  private readonly sessionPort: IdentitySessionPort;
+  constructor(
+    private readonly sessionPort: IdentitySessionPort,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<GetCurrentUserSessionResult>,
+  ) {}
 
-  constructor(sessionPort: IdentitySessionPort) {
-    this.sessionPort = sessionPort;
-  }
+  async execute(): Promise<Result<void, GetCurrentUserSessionApplicationError>> {
+    try {
+      const session = await this.sessionPort.getCurrentSession();
 
-  async execute(): Promise<AuthSessionDTO | null> {
-    return this.sessionPort.getCurrentSession();
+      this.output.present(session);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message
+          ? error.message
+          : 'Failed to execute GetCurrentUserSessionUseCase';
+
+      this.logger.error(
+        'GetCurrentUserSessionUseCase.execute failed',
+        error instanceof Error ? error : undefined,
+        {},
+      );
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as GetCurrentUserSessionApplicationError);
+    }
   }
 }

core/identity/application/use-cases/GetUserUseCase.ts

@@ -1,14 +1,58 @@
 import { User } from '../../domain/entities/User';
 import { IUserRepository } from '../../domain/repositories/IUserRepository';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+
+export type GetUserInput = {
+  userId: string;
+};
+
+export type GetUserResult = {
+  user: User;
+};
+
+export type GetUserErrorCode = 'USER_NOT_FOUND' | 'REPOSITORY_ERROR';
+
+export type GetUserApplicationError = ApplicationErrorCode<
+  GetUserErrorCode,
+  { message: string }
+>;
 
 export class GetUserUseCase {
-  constructor(private userRepo: IUserRepository) {}
+  constructor(
+    private readonly userRepo: IUserRepository,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<GetUserResult>,
+  ) {}
 
-  async execute(userId: string): Promise<User> {
-    const stored = await this.userRepo.findById(userId);
-    if (!stored) {
-      throw new Error('User not found');
+  async execute(input: GetUserInput): Promise<Result<void, GetUserApplicationError>> {
+    try {
+      const stored = await this.userRepo.findById(input.userId);
+      if (!stored) {
+        return Result.err({
+          code: 'USER_NOT_FOUND',
+          details: { message: 'User not found' },
+        } as GetUserApplicationError);
+      }
+
+      const user = User.fromStored(stored);
+      const result: GetUserResult = { user };
+      this.output.present(result);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message ? error.message : 'Failed to get user';
+
+      this.logger.error('GetUserUseCase.execute failed', error instanceof Error ? error : undefined, {
+        input,
+      });
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as GetUserApplicationError);
     }
-    return User.fromStored(stored);
   }
 }

core/identity/application/use-cases/HandleAuthCallbackUseCase.ts

@@ -3,19 +3,55 @@ import type { AuthSessionDTO } from '../dto/AuthSessionDTO';
 import type { AuthenticatedUserDTO } from '../dto/AuthenticatedUserDTO';
 import type { IdentityProviderPort } from '../ports/IdentityProviderPort';
 import type { IdentitySessionPort } from '../ports/IdentitySessionPort';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+
+export type HandleAuthCallbackInput = AuthCallbackCommandDTO;
+
+export type HandleAuthCallbackResult = AuthSessionDTO;
+
+export type HandleAuthCallbackErrorCode = 'REPOSITORY_ERROR';
+
+export type HandleAuthCallbackApplicationError = ApplicationErrorCode<
+  HandleAuthCallbackErrorCode,
+  { message: string }
+>;
 
 export class HandleAuthCallbackUseCase {
-  private readonly provider: IdentityProviderPort;
-  private readonly sessionPort: IdentitySessionPort;
+  constructor(
+    private readonly provider: IdentityProviderPort,
+    private readonly sessionPort: IdentitySessionPort,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<HandleAuthCallbackResult>,
+  ) {}
 
-  constructor(provider: IdentityProviderPort, sessionPort: IdentitySessionPort) {
-    this.provider = provider;
-    this.sessionPort = sessionPort;
-  }
+  async execute(input: HandleAuthCallbackInput): Promise<
+    Result<void, HandleAuthCallbackApplicationError>
+  > {
+    try {
+      const user: AuthenticatedUserDTO = await this.provider.completeAuth(input);
+      const session = await this.sessionPort.createSession(user);
 
-  async execute(command: AuthCallbackCommandDTO): Promise<AuthSessionDTO> {
-    const user: AuthenticatedUserDTO = await this.provider.completeAuth(command);
-    const session = await this.sessionPort.createSession(user);
-    return session;
+      this.output.present(session);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message
+          ? error.message
+          : 'Failed to execute HandleAuthCallbackUseCase';
+
+      this.logger.error(
+        'HandleAuthCallbackUseCase.execute failed',
+        error instanceof Error ? error : undefined,
+        { input },
+      );
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as HandleAuthCallbackApplicationError);
+    }
   }
 }

core/identity/application/use-cases/LoginUseCase.test.ts

@@ -1,9 +1,17 @@
 import { describe, it, expect, vi, type Mock } from 'vitest';
-import { LoginUseCase } from './LoginUseCase';
+import {
+  LoginUseCase,
+  type LoginInput,
+  type LoginResult,
+  type LoginErrorCode,
+} from './LoginUseCase';
 import { EmailAddress } from '../../domain/value-objects/EmailAddress';
 import type { IAuthRepository } from '../../domain/repositories/IAuthRepository';
 import type { IPasswordHashingService } from '../../domain/services/PasswordHashingService';
 import { User } from '../../domain/entities/User';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import { Result } from '@core/shared/application/Result';
 
 describe('LoginUseCase', () => {
   let authRepo: {
@@ -12,6 +20,8 @@ describe('LoginUseCase', () => {
   let passwordService: {
     verify: Mock;
   };
+  let logger: Logger & { error: Mock };
+  let output: UseCaseOutputPort<LoginResult> & { present: Mock };
   let useCase: LoginUseCase;
 
   beforeEach(() => {
@@ -21,16 +31,29 @@ describe('LoginUseCase', () => {
     passwordService = {
       verify: vi.fn(),
     };
+    logger = {
+      debug: vi.fn(),
+      info: vi.fn(),
+      warn: vi.fn(),
+      error: vi.fn(),
+    };
+    output = {
+      present: vi.fn(),
+    } as unknown as UseCaseOutputPort<LoginResult> & { present: Mock };
     useCase = new LoginUseCase(
       authRepo as unknown as IAuthRepository,
       passwordService as unknown as IPasswordHashingService,
+      logger,
+      output,
     );
   });
 
-  it('returns the user when credentials are valid', async () => {
-    const email = 'test@example.com';
-    const password = 'password123';
-    const emailVO = EmailAddress.create(email);
+  it('returns ok and presents user when credentials are valid', async () => {
+    const input: LoginInput = {
+      email: 'test@example.com',
+      password: 'password123',
+    };
+    const emailVO = EmailAddress.create(input.email);
 
     const user = User.create({
       id: { value: 'user-1' } as any,
@@ -43,25 +66,45 @@ describe('LoginUseCase', () => {
     authRepo.findByEmail.mockResolvedValue(user);
     passwordService.verify.mockResolvedValue(true);
 
-    const result = await useCase.execute(email, password);
+    const result: Result<void, ApplicationErrorCode<LoginErrorCode, { message: string }>> =
+      await useCase.execute(input);
+
+    expect(result.isOk()).toBe(true);
+    expect(result.unwrap()).toBeUndefined();
 
     expect(authRepo.findByEmail).toHaveBeenCalledWith(emailVO);
-    expect(passwordService.verify).toHaveBeenCalledWith(password, 'stored-hash');
-    expect(result).toBe(user);
+    expect(passwordService.verify).toHaveBeenCalledWith(input.password, 'stored-hash');
+
+    expect(output.present).toHaveBeenCalledTimes(1);
+    const presented = output.present.mock.calls[0]![0] as LoginResult;
+    expect(presented.user).toBe(user);
   });
 
-  it('throws when user is not found', async () => {
-    const email = 'missing@example.com';
+  it('returns INVALID_CREDENTIALS when user is not found', async () => {
+    const input: LoginInput = {
+      email: 'missing@example.com',
+      password: 'password123',
+    };
 
     authRepo.findByEmail.mockResolvedValue(null);
 
-    await expect(useCase.execute(email, 'password')).rejects.toThrow('Invalid credentials');
+    const result: Result<void, ApplicationErrorCode<LoginErrorCode, { message: string }>> =
+      await useCase.execute(input);
+
+    expect(result.isErr()).toBe(true);
+    const error = result.unwrapErr();
+
+    expect(error.code).toBe('INVALID_CREDENTIALS');
+    expect(error.details?.message).toBe('Invalid credentials');
+    expect(output.present).not.toHaveBeenCalled();
   });
 
-  it('throws when password is invalid', async () => {
-    const email = 'test@example.com';
-    const password = 'wrong-password';
-    const emailVO = EmailAddress.create(email);
+  it('returns INVALID_CREDENTIALS when password is invalid', async () => {
+    const input: LoginInput = {
+      email: 'test@example.com',
+      password: 'wrong-password',
+    };
+    const emailVO = EmailAddress.create(input.email);
 
     const user = User.create({
       id: { value: 'user-1' } as any,
@@ -74,8 +117,34 @@ describe('LoginUseCase', () => {
     authRepo.findByEmail.mockResolvedValue(user);
     passwordService.verify.mockResolvedValue(false);
 
-    await expect(useCase.execute(email, password)).rejects.toThrow('Invalid credentials');
-    expect(authRepo.findByEmail).toHaveBeenCalled();
-    expect(passwordService.verify).toHaveBeenCalled();
+    const result: Result<void, ApplicationErrorCode<LoginErrorCode, { message: string }>> =
+      await useCase.execute(input);
+
+    expect(result.isErr()).toBe(true);
+    const error = result.unwrapErr();
+
+    expect(error.code).toBe('INVALID_CREDENTIALS');
+    expect(error.details?.message).toBe('Invalid credentials');
+    expect(output.present).not.toHaveBeenCalled();
+  });
+
+  it('wraps unexpected errors as REPOSITORY_ERROR and logs them', async () => {
+    const input: LoginInput = {
+      email: 'test@example.com',
+      password: 'password123',
+    };
+
+    authRepo.findByEmail.mockRejectedValue(new Error('DB failure'));
+
+    const result: Result<void, ApplicationErrorCode<LoginErrorCode, { message: string }>> =
+      await useCase.execute(input);
+
+    expect(result.isErr()).toBe(true);
+    const error = result.unwrapErr();
+
+    expect(error.code).toBe('REPOSITORY_ERROR');
+    expect(error.details?.message).toBe('DB failure');
+    expect(output.present).not.toHaveBeenCalled();
+    expect(logger.error).toHaveBeenCalled();
   });
 });

core/identity/application/use-cases/LoginUseCase.ts

@@ -2,6 +2,22 @@ import { EmailAddress } from '../../domain/value-objects/EmailAddress';
 import { User } from '../../domain/entities/User';
 import { IAuthRepository } from '../../domain/repositories/IAuthRepository';
 import { IPasswordHashingService } from '../../domain/services/PasswordHashingService';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+
+export type LoginInput = {
+  email: string;
+  password: string;
+};
+
+export type LoginResult = {
+  user: User;
+};
+
+export type LoginErrorCode = 'INVALID_CREDENTIALS' | 'REPOSITORY_ERROR';
+
+export type LoginApplicationError = ApplicationErrorCode<LoginErrorCode, { message: string }>;
 
 /**
  * Application Use Case: LoginUseCase
@@ -10,20 +26,52 @@ import { IPasswordHashingService } from '../../domain/services/PasswordHashingSe
  */
 export class LoginUseCase {
   constructor(
-    private authRepo: IAuthRepository,
-    private passwordService: IPasswordHashingService
+    private readonly authRepo: IAuthRepository,
+    private readonly passwordService: IPasswordHashingService,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<LoginResult>,
   ) {}
 
-  async execute(email: string, password: string): Promise<User> {
-    const emailVO = EmailAddress.create(email);
-    const user = await this.authRepo.findByEmail(emailVO);
-    if (!user || !user.getPasswordHash()) {
-      throw new Error('Invalid credentials');
+  async execute(input: LoginInput): Promise<Result<void, LoginApplicationError>> {
+    try {
+      const emailVO = EmailAddress.create(input.email);
+      const user = await this.authRepo.findByEmail(emailVO);
+
+      if (!user || !user.getPasswordHash()) {
+        return Result.err({
+          code: 'INVALID_CREDENTIALS',
+          details: { message: 'Invalid credentials' },
+        } as LoginApplicationError);
+      }
+
+      const passwordHash = user.getPasswordHash()!;
+      const isValid = await this.passwordService.verify(input.password, passwordHash.value);
+
+      if (!isValid) {
+        return Result.err({
+          code: 'INVALID_CREDENTIALS',
+          details: { message: 'Invalid credentials' },
+        } as LoginApplicationError);
+      }
+
+      const result: LoginResult = { user };
+      this.output.present(result);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message
+          ? error.message
+          : 'Failed to execute LoginUseCase';
+
+      this.logger.error('LoginUseCase.execute failed', error instanceof Error ? error : undefined, {
+        input,
+      });
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as LoginApplicationError);
     }
-    const isValid = await this.passwordService.verify(password, user.getPasswordHash()!.value);
-    if (!isValid) {
-      throw new Error('Invalid credentials');
-    }
-    return user;
   }
 }

core/identity/application/use-cases/LoginWithEmailUseCase.test.ts

@@ -1,8 +1,15 @@
 import { describe, it, expect, vi, type Mock } from 'vitest';
-import { LoginWithEmailUseCase, type LoginCommandDTO } from './LoginWithEmailUseCase';
+import {
+  LoginWithEmailUseCase,
+  type LoginWithEmailInput,
+  type LoginWithEmailResult,
+  type LoginWithEmailErrorCode,
+} from './LoginWithEmailUseCase';
 import type { IUserRepository, StoredUser } from '../../domain/repositories/IUserRepository';
 import type { IdentitySessionPort } from '../ports/IdentitySessionPort';
-import type { AuthSessionDTO } from '../dto/AuthSessionDTO';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import { Result } from '@core/shared/application/Result';
 
 describe('LoginWithEmailUseCase', () => {
   let userRepository: {
@@ -13,6 +20,8 @@ describe('LoginWithEmailUseCase', () => {
     getCurrentSession: Mock;
     clearSession: Mock;
   };
+  let logger: Logger & { error: Mock };
+  let output: UseCaseOutputPort<LoginWithEmailResult> & { present: Mock };
   let useCase: LoginWithEmailUseCase;
 
   beforeEach(() => {
@@ -24,14 +33,26 @@ describe('LoginWithEmailUseCase', () => {
       getCurrentSession: vi.fn(),
       clearSession: vi.fn(),
     };
+    logger = {
+      debug: vi.fn(),
+      info: vi.fn(),
+      warn: vi.fn(),
+      error: vi.fn(),
+    } as unknown as Logger & { error: Mock };
+    output = {
+      present: vi.fn(),
+    } as unknown as UseCaseOutputPort<LoginWithEmailResult> & { present: Mock };
+
     useCase = new LoginWithEmailUseCase(
       userRepository as unknown as IUserRepository,
       sessionPort as unknown as IdentitySessionPort,
+      logger,
+      output,
     );
   });
 
-  it('creates a session for valid credentials', async () => {
-    const command: LoginCommandDTO = {
+  it('returns ok and presents session result for valid credentials', async () => {
+    const input: LoginWithEmailInput = {
       email: 'Test@Example.com',
       password: 'password123',
     };
@@ -45,7 +66,7 @@ describe('LoginWithEmailUseCase', () => {
       createdAt: new Date(),
     };
 
-    const session: AuthSessionDTO = {
+    const session = {
       user: {
         id: storedUser.id,
         email: storedUser.email,
@@ -59,35 +80,59 @@ describe('LoginWithEmailUseCase', () => {
     userRepository.findByEmail.mockResolvedValue(storedUser);
     sessionPort.createSession.mockResolvedValue(session);
 
-    const result = await useCase.execute(command);
+    const result: Result<void, ApplicationErrorCode<LoginWithEmailErrorCode, { message: string }>> =
+      await useCase.execute(input);
+
+    expect(result.isOk()).toBe(true);
+    expect(result.unwrap()).toBeUndefined();
 
     expect(userRepository.findByEmail).toHaveBeenCalledWith('test@example.com');
     expect(sessionPort.createSession).toHaveBeenCalledWith({
       id: storedUser.id,
       email: storedUser.email,
       displayName: storedUser.displayName,
+      primaryDriverId: undefined,
     });
-    expect(result).toEqual(session);
+
+    expect(output.present).toHaveBeenCalledTimes(1);
+    const presented = output.present.mock.calls[0]![0] as LoginWithEmailResult;
+    expect(presented.sessionToken).toBe('token-123');
+    expect(presented.userId).toBe(storedUser.id);
+    expect(presented.displayName).toBe(storedUser.displayName);
+    expect(presented.email).toBe(storedUser.email);
   });
 
-  it('throws when email or password is missing', async () => {
-    await expect(useCase.execute({ email: '', password: 'x' })).rejects.toThrow('Email and password are required');
-    await expect(useCase.execute({ email: 'a@example.com', password: '' })).rejects.toThrow('Email and password are required');
+  it('returns INVALID_INPUT when email or password is missing', async () => {
+    const result1 = await useCase.execute({ email: '', password: 'x' });
+    const result2 = await useCase.execute({ email: 'a@example.com', password: '' });
+
+    expect(result1.isErr()).toBe(true);
+    expect(result1.unwrapErr().code).toBe('INVALID_INPUT');
+    expect(result2.isErr()).toBe(true);
+    expect(result2.unwrapErr().code).toBe('INVALID_INPUT');
+    expect(output.present).not.toHaveBeenCalled();
   });
 
-  it('throws when user does not exist', async () => {
-    const command: LoginCommandDTO = {
+  it('returns INVALID_CREDENTIALS when user does not exist', async () => {
+    const input: LoginWithEmailInput = {
       email: 'missing@example.com',
       password: 'password',
     };
 
     userRepository.findByEmail.mockResolvedValue(null);
 
-    await expect(useCase.execute(command)).rejects.toThrow('Invalid email or password');
+    const result: Result<void, ApplicationErrorCode<LoginWithEmailErrorCode, { message: string }>> =
+      await useCase.execute(input);
+
+    expect(result.isErr()).toBe(true);
+    const error = result.unwrapErr();
+    expect(error.code).toBe('INVALID_CREDENTIALS');
+    expect(error.details.message).toBe('Invalid email or password');
+    expect(output.present).not.toHaveBeenCalled();
   });
 
-  it('throws when password is invalid', async () => {
-    const command: LoginCommandDTO = {
+  it('returns INVALID_CREDENTIALS when password is invalid', async () => {
+    const input: LoginWithEmailInput = {
       email: 'test@example.com',
       password: 'wrong',
     };
@@ -103,6 +148,33 @@ describe('LoginWithEmailUseCase', () => {
 
     userRepository.findByEmail.mockResolvedValue(storedUser);
 
-    await expect(useCase.execute(command)).rejects.toThrow('Invalid email or password');
+    const result: Result<void, ApplicationErrorCode<LoginWithEmailErrorCode, { message: string }>> =
+      await useCase.execute(input);
+
+    expect(result.isErr()).toBe(true);
+    const error = result.unwrapErr();
+    expect(error.code).toBe('INVALID_CREDENTIALS');
+    expect(error.details.message).toBe('Invalid email or password');
+    expect(output.present).not.toHaveBeenCalled();
+  });
+
+  it('wraps unexpected errors as REPOSITORY_ERROR and logs them', async () => {
+    const input: LoginWithEmailInput = {
+      email: 'test@example.com',
+      password: 'password123',
+    };
+
+    userRepository.findByEmail.mockRejectedValue(new Error('DB failure'));
+
+    const result: Result<void, ApplicationErrorCode<LoginWithEmailErrorCode, { message: string }>> =
+      await useCase.execute(input);
+
+    expect(result.isErr()).toBe(true);
+    const error = result.unwrapErr();
+
+    expect(error.code).toBe('REPOSITORY_ERROR');
+    expect(error.details.message).toBe('DB failure');
+    expect(output.present).not.toHaveBeenCalled();
+    expect(logger.error).toHaveBeenCalled();
   });
 });

core/identity/application/use-cases/LoginWithEmailUseCase.ts

@@ -1,56 +1,112 @@
 /**
  * Login with Email Use Case
- * 
+ *
  * Authenticates a user with email and password.
  */
 
 import type { IUserRepository } from '../../domain/repositories/IUserRepository';
-import type { AuthenticatedUserDTO } from '../dto/AuthenticatedUserDTO';
-import type { AuthSessionDTO } from '../dto/AuthSessionDTO';
 import type { IdentitySessionPort } from '../ports/IdentitySessionPort';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
 
-export interface LoginCommandDTO {
+export type LoginWithEmailInput = {
   email: string;
   password: string;
-}
+};
+
+export type LoginWithEmailResult = {
+  sessionToken: string;
+  userId: string;
+  displayName: string;
+  email?: string;
+  primaryDriverId?: string;
+  issuedAt: number;
+  expiresAt: number;
+};
+
+export type LoginWithEmailErrorCode =
+  | 'INVALID_INPUT'
+  | 'INVALID_CREDENTIALS'
+  | 'REPOSITORY_ERROR';
+
+export type LoginWithEmailApplicationError = ApplicationErrorCode<
+  LoginWithEmailErrorCode,
+  { message: string }
+>;
 
 export class LoginWithEmailUseCase {
   constructor(
     private readonly userRepository: IUserRepository,
     private readonly sessionPort: IdentitySessionPort,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<LoginWithEmailResult>,
   ) {}
 
-  async execute(command: LoginCommandDTO): Promise<AuthSessionDTO> {
-    // Validate inputs
-    if (!command.email || !command.password) {
-      throw new Error('Email and password are required');
+  async execute(input: LoginWithEmailInput): Promise<Result<void, LoginWithEmailApplicationError>> {
+    try {
+      if (!input.email || !input.password) {
+        return Result.err({
+          code: 'INVALID_INPUT',
+          details: { message: 'Email and password are required' },
+        } as LoginWithEmailApplicationError);
+      }
+
+      const normalizedEmail = input.email.toLowerCase().trim();
+
+      const user = await this.userRepository.findByEmail(normalizedEmail);
+      if (!user) {
+        return Result.err({
+          code: 'INVALID_CREDENTIALS',
+          details: { message: 'Invalid email or password' },
+        } as LoginWithEmailApplicationError);
+      }
+
+      const passwordHash = await this.hashPassword(input.password, user.salt);
+      if (passwordHash !== user.passwordHash) {
+        return Result.err({
+          code: 'INVALID_CREDENTIALS',
+          details: { message: 'Invalid email or password' },
+        } as LoginWithEmailApplicationError);
+      }
+
+      const session = await this.sessionPort.createSession({
+        id: user.id,
+        displayName: user.displayName,
+        email: user.email,
+        primaryDriverId: user.primaryDriverId,
+      } as any);
+
+      const result: LoginWithEmailResult = {
+        sessionToken: (session as any).token,
+        userId: (session as any).user.id,
+        displayName: (session as any).user.displayName,
+        email: (session as any).user.email,
+        primaryDriverId: (session as any).user.primaryDriverId,
+        issuedAt: (session as any).issuedAt,
+        expiresAt: (session as any).expiresAt,
+      };
+
+      this.output.present(result);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message
+          ? error.message
+          : 'Failed to execute LoginWithEmailUseCase';
+
+      this.logger.error(
+        'LoginWithEmailUseCase.execute failed',
+        error instanceof Error ? error : undefined,
+        { input },
+      );
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as LoginWithEmailApplicationError);
     }
-
-    // Find user by email
-    const user = await this.userRepository.findByEmail(command.email.toLowerCase().trim());
-    if (!user) {
-      throw new Error('Invalid email or password');
-    }
-
-    // Verify password
-    const passwordHash = await this.hashPassword(command.password, user.salt);
-    if (passwordHash !== user.passwordHash) {
-      throw new Error('Invalid email or password');
-    }
-
-    // Create session
-    const authenticatedUserBase: AuthenticatedUserDTO = {
-      id: user.id,
-      displayName: user.displayName,
-      email: user.email,
-    };
-
-    const authenticatedUser: AuthenticatedUserDTO =
-      user.primaryDriverId !== undefined
-        ? { ...authenticatedUserBase, primaryDriverId: user.primaryDriverId }
-        : authenticatedUserBase;
-
-    return this.sessionPort.createSession(authenticatedUser);
   }
 
   private async hashPassword(password: string, salt: string): Promise<string> {

core/identity/application/use-cases/LogoutUseCase.test.ts

@@ -1,6 +1,9 @@
 import { describe, it, expect, vi, type Mock } from 'vitest';
-import { LogoutUseCase } from './LogoutUseCase';
+import { LogoutUseCase, type LogoutResult, type LogoutErrorCode } from './LogoutUseCase';
 import type { IdentitySessionPort } from '../ports/IdentitySessionPort';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import { Result } from '@core/shared/application/Result';
 
 describe('LogoutUseCase', () => {
   let sessionPort: {
@@ -8,6 +11,8 @@ describe('LogoutUseCase', () => {
     getCurrentSession: Mock;
     createSession: Mock;
   };
+  let logger: Logger & { error: Mock };
+  let output: UseCaseOutputPort<LogoutResult> & { present: Mock };
   let useCase: LogoutUseCase;
 
   beforeEach(() => {
@@ -17,12 +22,49 @@ describe('LogoutUseCase', () => {
       createSession: vi.fn(),
     };
 
-    useCase = new LogoutUseCase(sessionPort as unknown as IdentitySessionPort);
+    logger = {
+      debug: vi.fn(),
+      info: vi.fn(),
+      warn: vi.fn(),
+      error: vi.fn(),
+    } as unknown as Logger & { error: Mock };
+
+    output = {
+      present: vi.fn(),
+    } as unknown as UseCaseOutputPort<LogoutResult> & { present: Mock };
+
+    useCase = new LogoutUseCase(
+      sessionPort as unknown as IdentitySessionPort,
+      logger,
+      output,
+    );
   });
 
-  it('clears the current session', async () => {
-    await useCase.execute();
+  it('clears the current session and presents success', async () => {
+    const result: Result<void, ApplicationErrorCode<LogoutErrorCode, { message: string }>> =
+      await useCase.execute();
+
+    expect(result.isOk()).toBe(true);
+    expect(result.unwrap()).toBeUndefined();
 
     expect(sessionPort.clearSession).toHaveBeenCalledTimes(1);
+    expect(output.present).toHaveBeenCalledTimes(1);
+    expect(output.present).toHaveBeenCalledWith({ success: true });
+  });
+
+  it('wraps unexpected errors as REPOSITORY_ERROR and logs them', async () => {
+    const error = new Error('Session clear failed');
+    sessionPort.clearSession.mockRejectedValue(error);
+
+    const result: Result<void, ApplicationErrorCode<LogoutErrorCode, { message: string }>> =
+      await useCase.execute();
+
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr();
+    expect(err.code).toBe('REPOSITORY_ERROR');
+    expect(err.details.message).toBe('Session clear failed');
+
+    expect(output.present).not.toHaveBeenCalled();
+    expect(logger.error).toHaveBeenCalled();
   });
 });

core/identity/application/use-cases/LogoutUseCase.ts

@@ -1,13 +1,53 @@
 import type { IdentitySessionPort } from '../ports/IdentitySessionPort';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+
+export type LogoutInput = {};
+
+export type LogoutResult = {
+  success: boolean;
+};
+
+export type LogoutErrorCode = 'REPOSITORY_ERROR';
+
+export type LogoutApplicationError = ApplicationErrorCode<LogoutErrorCode, { message: string }>;
 
 export class LogoutUseCase {
   private readonly sessionPort: IdentitySessionPort;
 
-  constructor(sessionPort: IdentitySessionPort) {
+  constructor(
+    sessionPort: IdentitySessionPort,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<LogoutResult>,
+  ) {
     this.sessionPort = sessionPort;
   }
 
-  async execute(): Promise<void> {
-    await this.sessionPort.clearSession();
+  async execute(): Promise<Result<void, LogoutApplicationError>> {
+    try {
+      await this.sessionPort.clearSession();
+
+      const result: LogoutResult = { success: true };
+      this.output.present(result);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message
+          ? error.message
+          : 'Failed to execute LogoutUseCase';
+
+      this.logger.error(
+        'LogoutUseCase.execute failed',
+        error instanceof Error ? error : undefined,
+        {},
+      );
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as LogoutApplicationError);
+    }
   }
 }

core/identity/application/use-cases/SignupUseCase.ts

@@ -3,6 +3,23 @@ import { UserId } from '../../domain/value-objects/UserId';
 import { User } from '../../domain/entities/User';
 import { IAuthRepository } from '../../domain/repositories/IAuthRepository';
 import { IPasswordHashingService } from '../../domain/services/PasswordHashingService';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+
+export type SignupInput = {
+  email: string;
+  password: string;
+  displayName: string;
+};
+
+export type SignupResult = {
+  user: User;
+};
+
+export type SignupErrorCode = 'USER_ALREADY_EXISTS' | 'REPOSITORY_ERROR';
+
+export type SignupApplicationError = ApplicationErrorCode<SignupErrorCode, { message: string }>;
 
 /**
  * Application Use Case: SignupUseCase
@@ -11,31 +28,56 @@ import { IPasswordHashingService } from '../../domain/services/PasswordHashingSe
  */
 export class SignupUseCase {
   constructor(
-    private authRepo: IAuthRepository,
-    private passwordService: IPasswordHashingService
+    private readonly authRepo: IAuthRepository,
+    private readonly passwordService: IPasswordHashingService,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<SignupResult>,
   ) {}
 
-  async execute(email: string, password: string, displayName: string): Promise<User> {
-    const emailVO = EmailAddress.create(email);
+  async execute(input: SignupInput): Promise<Result<void, SignupApplicationError>> {
+    try {
+      const emailVO = EmailAddress.create(input.email);
 
-    // Check if user already exists
-    const existingUser = await this.authRepo.findByEmail(emailVO);
-    if (existingUser) {
-      throw new Error('User already exists');
+      const existingUser = await this.authRepo.findByEmail(emailVO);
+      if (existingUser) {
+        return Result.err({
+          code: 'USER_ALREADY_EXISTS',
+          details: { message: 'User already exists' },
+        } as SignupApplicationError);
+      }
+
+      const hashedPassword = await this.passwordService.hash(input.password);
+      const passwordHashModule = await import('../../domain/value-objects/PasswordHash');
+      const passwordHash = passwordHashModule.PasswordHash.fromHash(hashedPassword);
+
+      const userId = UserId.create();
+      const user = User.create({
+        id: userId,
+        displayName: input.displayName,
+        email: emailVO.value,
+        passwordHash,
+      });
+
+      await this.authRepo.save(user);
+
+      const result: SignupResult = { user };
+      this.output.present(result);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message
+          ? error.message
+          : 'Failed to execute SignupUseCase';
+
+      this.logger.error('SignupUseCase.execute failed', error instanceof Error ? error : undefined, {
+        input,
+      });
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as SignupApplicationError);
     }
-
-    const hashedPassword = await this.passwordService.hash(password);
-    const passwordHash = await import('../../domain/value-objects/PasswordHash').then(m => m.PasswordHash.fromHash(hashedPassword));
-
-    const userId = UserId.create();
-    const user = User.create({
-      id: userId,
-      displayName,
-      email: emailVO.value,
-      passwordHash,
-    });
-
-    await this.authRepo.save(user);
-    return user;
   }
 }

core/identity/application/use-cases/SignupWithEmailUseCase.ts

@@ -1,84 +1,145 @@
 /**
  * Signup with Email Use Case
- * 
+ *
  * Creates a new user account with email and password.
  */
 
 import type { IUserRepository, StoredUser } from '../../domain/repositories/IUserRepository';
 import type { AuthenticatedUserDTO } from '../dto/AuthenticatedUserDTO';
-import type { AuthSessionDTO } from '../dto/AuthSessionDTO';
 import type { IdentitySessionPort } from '../ports/IdentitySessionPort';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
 
-export interface SignupCommandDTO {
+export type SignupWithEmailInput = {
   email: string;
   password: string;
   displayName: string;
-}
+};
 
-export interface SignupResultDTO {
-  session: AuthSessionDTO;
+export type SignupWithEmailResult = {
+  sessionToken: string;
+  userId: string;
+  displayName: string;
+  email: string;
+  createdAt: Date;
   isNewUser: boolean;
-}
+};
+
+export type SignupWithEmailErrorCode =
+  | 'INVALID_EMAIL_FORMAT'
+  | 'WEAK_PASSWORD'
+  | 'INVALID_DISPLAY_NAME'
+  | 'EMAIL_ALREADY_EXISTS'
+  | 'REPOSITORY_ERROR';
+
+export type SignupWithEmailApplicationError = ApplicationErrorCode<
+  SignupWithEmailErrorCode,
+  { message: string }
+>;
 
 export class SignupWithEmailUseCase {
   constructor(
     private readonly userRepository: IUserRepository,
     private readonly sessionPort: IdentitySessionPort,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<SignupWithEmailResult>,
   ) {}
 
-  async execute(command: SignupCommandDTO): Promise<SignupResultDTO> {
+  async execute(input: SignupWithEmailInput): Promise<
+    Result<void, SignupWithEmailApplicationError>
+  > {
     // Validate email format
     const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
-    if (!emailRegex.test(command.email)) {
-      throw new Error('Invalid email format');
+    if (!emailRegex.test(input.email)) {
+      return Result.err({
+        code: 'INVALID_EMAIL_FORMAT',
+        details: { message: 'Invalid email format' },
+      } as SignupWithEmailApplicationError);
     }
 
     // Validate password strength
-    if (command.password.length < 8) {
-      throw new Error('Password must be at least 8 characters');
+    if (input.password.length < 8) {
+      return Result.err({
+        code: 'WEAK_PASSWORD',
+        details: { message: 'Password must be at least 8 characters' },
+      } as SignupWithEmailApplicationError);
     }
 
     // Validate display name
-    if (!command.displayName || command.displayName.trim().length < 2) {
-      throw new Error('Display name must be at least 2 characters');
+    if (!input.displayName || input.displayName.trim().length < 2) {
+      return Result.err({
+        code: 'INVALID_DISPLAY_NAME',
+        details: { message: 'Display name must be at least 2 characters' },
+      } as SignupWithEmailApplicationError);
     }
 
     // Check if email already exists
-    const existingUser = await this.userRepository.findByEmail(command.email);
+    const existingUser = await this.userRepository.findByEmail(input.email);
     if (existingUser) {
-      throw new Error('An account with this email already exists');
+      return Result.err({
+        code: 'EMAIL_ALREADY_EXISTS',
+        details: { message: 'An account with this email already exists' },
+      } as SignupWithEmailApplicationError);
     }
 
-    // Hash password (simple hash for demo - in production use bcrypt)
-    const salt = this.generateSalt();
-    const passwordHash = await this.hashPassword(command.password, salt);
+    try {
+      // Hash password (simple hash for demo - in production use bcrypt)
+      const salt = this.generateSalt();
+      const passwordHash = await this.hashPassword(input.password, salt);
 
-    // Create user
-    const userId = this.generateUserId();
-    const newUser: StoredUser = {
-      id: userId,
-      email: command.email.toLowerCase().trim(),
-      displayName: command.displayName.trim(),
-      passwordHash,
-      salt,
-      createdAt: new Date(),
-    };
+      // Create user
+      const userId = this.generateUserId();
+      const createdAt = new Date();
+      const newUser: StoredUser = {
+        id: userId,
+        email: input.email.toLowerCase().trim(),
+        displayName: input.displayName.trim(),
+        passwordHash,
+        salt,
+        createdAt,
+      };
 
-    await this.userRepository.create(newUser);
+      await this.userRepository.create(newUser);
 
-    // Create session
-    const authenticatedUser: AuthenticatedUserDTO = {
-      id: newUser.id,
-      displayName: newUser.displayName,
-      email: newUser.email,
-    };
+      // Create session
+      const authenticatedUser: AuthenticatedUserDTO = {
+        id: newUser.id,
+        displayName: newUser.displayName,
+        email: newUser.email,
+      };
 
-    const session = await this.sessionPort.createSession(authenticatedUser);
+      const session = await this.sessionPort.createSession(authenticatedUser);
 
-    return {
-      session,
-      isNewUser: true,
-    };
+      const result: SignupWithEmailResult = {
+        sessionToken: session.token,
+        userId: session.user.id,
+        displayName: session.user.displayName,
+        email: session.user.email ?? newUser.email,
+        createdAt,
+        isNewUser: true,
+      };
+
+      this.output.present(result);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message
+          ? error.message
+          : 'Failed to execute SignupWithEmailUseCase';
+
+      this.logger.error(
+        'SignupWithEmailUseCase.execute failed',
+        error instanceof Error ? error : undefined,
+        { input },
+      );
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as SignupWithEmailApplicationError);
+    }
   }
 
   private generateSalt(): string {

core/identity/application/use-cases/StartAuthUseCase.test.ts

@@ -1,12 +1,21 @@
 import { describe, it, expect, vi, type Mock } from 'vitest';
-import { StartAuthUseCase } from './StartAuthUseCase';
+import {
+  StartAuthUseCase,
+  type StartAuthInput,
+  type StartAuthResult,
+  type StartAuthErrorCode,
+} from './StartAuthUseCase';
 import type { IdentityProviderPort } from '../ports/IdentityProviderPort';
-import type { StartAuthCommandDTO } from '../dto/StartAuthCommandDTO';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import { Result } from '@core/shared/application/Result';
 
 describe('StartAuthUseCase', () => {
   let provider: {
     startAuth: Mock;
   };
+  let logger: Logger & { error: Mock };
+  let output: UseCaseOutputPort<StartAuthResult> & { present: Mock };
   let useCase: StartAuthUseCase;
 
   beforeEach(() => {
@@ -14,22 +23,67 @@ describe('StartAuthUseCase', () => {
       startAuth: vi.fn(),
     };
 
-    useCase = new StartAuthUseCase(provider as unknown as IdentityProviderPort);
+    logger = {
+      debug: vi.fn(),
+      info: vi.fn(),
+      warn: vi.fn(),
+      error: vi.fn(),
+    } as unknown as Logger & { error: Mock };
+
+    output = {
+      present: vi.fn(),
+    } as unknown as UseCaseOutputPort<StartAuthResult> & { present: Mock };
+
+    useCase = new StartAuthUseCase(
+      provider as unknown as IdentityProviderPort,
+      logger,
+      output,
+    );
   });
 
-  it('delegates to the identity provider to start auth', async () => {
-    const command: StartAuthCommandDTO = {
-      redirectUri: 'https://app/callback',
-      provider: 'demo',
+  it('returns ok and presents redirect when provider call succeeds', async () => {
+    const input: StartAuthInput = {
+      provider: 'IRACING_DEMO' as any,
+      returnTo: 'https://app/callback',
     };
 
     const expected = { redirectUrl: 'https://auth/redirect', state: 'state-123' };
 
     provider.startAuth.mockResolvedValue(expected);
 
-    const result = await useCase.execute(command);
+    const result: Result<void, ApplicationErrorCode<StartAuthErrorCode, { message: string }>> =
+      await useCase.execute(input);
 
-    expect(provider.startAuth).toHaveBeenCalledWith(command);
-    expect(result).toEqual(expected);
+    expect(result.isOk()).toBe(true);
+    expect(result.unwrap()).toBeUndefined();
+
+    expect(provider.startAuth).toHaveBeenCalledWith({
+      provider: input.provider,
+      returnTo: input.returnTo,
+    });
+
+    expect(output.present).toHaveBeenCalledTimes(1);
+    const presented = output.present.mock.calls[0]![0] as StartAuthResult;
+    expect(presented).toEqual(expected);
+  });
+
+  it('wraps unexpected errors as REPOSITORY_ERROR and logs them', async () => {
+    const input: StartAuthInput = {
+      provider: 'IRACING_DEMO' as any,
+      returnTo: 'https://app/callback',
+    };
+
+    provider.startAuth.mockRejectedValue(new Error('Provider failure'));
+
+    const result: Result<void, ApplicationErrorCode<StartAuthErrorCode, { message: string }>> =
+      await useCase.execute(input);
+
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr();
+    expect(err.code).toBe('REPOSITORY_ERROR');
+    expect(err.details.message).toBe('Provider failure');
+
+    expect(output.present).not.toHaveBeenCalled();
+    expect(logger.error).toHaveBeenCalled();
   });
 });

core/identity/application/use-cases/StartAuthUseCase.ts

@@ -1,14 +1,63 @@
 import type { StartAuthCommandDTO } from '../dto/StartAuthCommandDTO';
 import type { IdentityProviderPort } from '../ports/IdentityProviderPort';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
+
+export type StartAuthInput = {
+  provider: StartAuthCommandDTO['provider'];
+  returnTo?: StartAuthCommandDTO['returnTo'];
+};
+
+export type StartAuthResult = {
+  redirectUrl: string;
+  state: string;
+};
+
+export type StartAuthErrorCode = 'REPOSITORY_ERROR';
+
+export type StartAuthApplicationError = ApplicationErrorCode<StartAuthErrorCode, { message: string }>;
 
 export class StartAuthUseCase {
-  private readonly provider: IdentityProviderPort;
+  constructor(
+    private readonly provider: IdentityProviderPort,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<StartAuthResult>,
+  ) {}
 
-  constructor(provider: IdentityProviderPort) {
-    this.provider = provider;
-  }
+  async execute(input: StartAuthInput): Promise<Result<void, StartAuthApplicationError>> {
+    try {
+      const command: StartAuthCommandDTO = input.returnTo
+        ? {
+            provider: input.provider,
+            returnTo: input.returnTo,
+          }
+        : {
+            provider: input.provider,
+          };
 
-  async execute(command: StartAuthCommandDTO): Promise<{ redirectUrl: string; state: string }> {
-    return this.provider.startAuth(command);
+      const { redirectUrl, state } = await this.provider.startAuth(command);
+
+      const result: StartAuthResult = { redirectUrl, state };
+      this.output.present(result);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message
+          ? error.message
+          : 'Failed to execute StartAuthUseCase';
+
+      this.logger.error(
+        'StartAuthUseCase.execute failed',
+        error instanceof Error ? error : undefined,
+        { input },
+      );
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as StartAuthApplicationError);
+    }
   }
 }

core/identity/application/use-cases/achievement/CreateAchievementUseCase.ts

@@ -1,16 +1,60 @@
 import { Achievement, AchievementProps } from '@core/identity/domain/entities/Achievement';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
+import type { UseCaseOutputPort, Logger } from '@core/shared/application';
 
 export interface IAchievementRepository {
   save(achievement: Achievement): Promise<void>;
   findById(id: string): Promise<Achievement | null>;
 }
 
-export class CreateAchievementUseCase {
-  constructor(private readonly achievementRepository: IAchievementRepository) {}
+export type CreateAchievementInput = Omit<AchievementProps, 'createdAt'>;
 
-  async execute(props: Omit<AchievementProps, 'createdAt'>): Promise<Achievement> {
-    const achievement = Achievement.create(props);
-    await this.achievementRepository.save(achievement);
-    return achievement;
+export type CreateAchievementResult = {
+  achievement: Achievement;
+};
+
+export type CreateAchievementErrorCode = 'REPOSITORY_ERROR';
+
+export type CreateAchievementApplicationError = ApplicationErrorCode<
+  CreateAchievementErrorCode,
+  { message: string }
+>;
+
+export class CreateAchievementUseCase {
+  constructor(
+    private readonly achievementRepository: IAchievementRepository,
+    private readonly logger: Logger,
+    private readonly output: UseCaseOutputPort<CreateAchievementResult>,
+  ) {}
+
+  async execute(input: CreateAchievementInput): Promise<
+    Result<void, CreateAchievementApplicationError>
+  > {
+    try {
+      const achievement = Achievement.create(input);
+      await this.achievementRepository.save(achievement);
+
+      const result: CreateAchievementResult = { achievement };
+      this.output.present(result);
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const message =
+        error instanceof Error && error.message
+          ? error.message
+          : 'Failed to execute CreateAchievementUseCase';
+
+      this.logger.error(
+        'CreateAchievementUseCase.execute failed',
+        error instanceof Error ? error : undefined,
+        { input },
+      );
+
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message },
+      } as CreateAchievementApplicationError);
+    }
   }
 }

core/league/application/use-cases/GetLeagueStandingsUseCase.ts

@@ -1,3 +1,5 @@
+// TODO is this even used? either remove or it must be within racing domain
+
 export interface GetLeagueStandingsUseCase {
   execute(leagueId: string): Promise<LeagueStandingsViewModel>;
 }

core/league/application/use-cases/GetLeagueStandingsUseCaseImpl.ts

@@ -1,5 +1,7 @@
-import { GetLeagueStandingsUseCase, LeagueStandingsViewModel, StandingItemViewModel } from './GetLeagueStandingsUseCase';
 import { ILeagueStandingsRepository, RawStanding } from '../ports/ILeagueStandingsRepository';
+import { GetLeagueStandingsUseCase, LeagueStandingsViewModel, StandingItemViewModel } from './GetLeagueStandingsUseCase';
+
+// TODO is this even used? either remove or it must be within racing domain
 
 export class GetLeagueStandingsUseCaseImpl implements GetLeagueStandingsUseCase {
   constructor(private repository: ILeagueStandingsRepository) {}

core/media/application/use-cases/DeleteMediaUseCase.test.ts

@@ -1,12 +1,23 @@
 import { describe, it, expect, vi, type Mock } from 'vitest';
-import { DeleteMediaUseCase } from './DeleteMediaUseCase';
+import {
+  DeleteMediaUseCase,
+  type DeleteMediaInput,
+  type DeleteMediaResult,
+  type DeleteMediaErrorCode,
+} from './DeleteMediaUseCase';
 import type { IMediaRepository } from '../../domain/repositories/IMediaRepository';
 import type { MediaStoragePort } from '../ports/MediaStoragePort';
-import type { IDeleteMediaPresenter } from '../presenters/IDeleteMediaPresenter';
-import type { Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import { Media } from '../../domain/entities/Media';
 import { MediaUrl } from '../../domain/value-objects/MediaUrl';
 
+interface TestOutputPort extends UseCaseOutputPort<DeleteMediaResult> {
+  present: Mock;
+  result?: DeleteMediaResult;
+}
+
 describe('DeleteMediaUseCase', () => {
   let mediaRepo: {
     findById: Mock;
@@ -16,7 +27,7 @@ describe('DeleteMediaUseCase', () => {
     deleteMedia: Mock;
   };
   let logger: Logger;
-  let presenter: IDeleteMediaPresenter & { result?: any };
+  let output: TestOutputPort;
   let useCase: DeleteMediaUseCase;
 
   beforeEach(() => {
@@ -36,29 +47,35 @@ describe('DeleteMediaUseCase', () => {
       error: vi.fn(),
     } as unknown as Logger;
 
-    presenter = {
-      present: vi.fn((result) => {
-        (presenter as any).result = result;
+    output = {
+      present: vi.fn((result: DeleteMediaResult) => {
+        output.result = result;
       }),
-    } as unknown as IDeleteMediaPresenter & { result?: any };
+    } as unknown as TestOutputPort;
 
     useCase = new DeleteMediaUseCase(
       mediaRepo as unknown as IMediaRepository,
       mediaStorage as unknown as MediaStoragePort,
+      output,
       logger,
     );
   });
 
-  it('returns error result when media is not found', async () => {
+  it('returns MEDIA_NOT_FOUND when media is not found', async () => {
     mediaRepo.findById.mockResolvedValue(null);
 
-    await useCase.execute({ mediaId: 'missing' }, presenter);
+    const input: DeleteMediaInput = { mediaId: 'missing' };
+    const result = await useCase.execute(input);
 
     expect(mediaRepo.findById).toHaveBeenCalledWith('missing');
-    expect((presenter.present as unknown as Mock)).toHaveBeenCalledWith({
-      success: false,
-      errorMessage: 'Media not found',
-    });
+    expect(result).toBeInstanceOf(Result);
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr() as ApplicationErrorCode<
+      DeleteMediaErrorCode,
+      { message: string }
+    >;
+    expect(err.code).toBe('MEDIA_NOT_FOUND');
+    expect(output.present).not.toHaveBeenCalled();
   });
 
   it('deletes media from storage and repository on success', async () => {
@@ -68,30 +85,39 @@ describe('DeleteMediaUseCase', () => {
       originalName: 'file.png',
       mimeType: 'image/png',
       size: 123,
-      url: MediaUrl.create('https://example.com/file.png'),
+      url: 'https://example.com/file.png',
       type: 'image',
       uploadedBy: 'user-1',
     });
 
     mediaRepo.findById.mockResolvedValue(media);
 
-    await useCase.execute({ mediaId: 'media-1' }, presenter);
+    const input: DeleteMediaInput = { mediaId: 'media-1' };
+    const result = await useCase.execute(input);
 
+    expect(result.isOk()).toBe(true);
     expect(mediaRepo.findById).toHaveBeenCalledWith('media-1');
     expect(mediaStorage.deleteMedia).toHaveBeenCalledWith(media.url.value);
     expect(mediaRepo.delete).toHaveBeenCalledWith('media-1');
-    expect((presenter.present as unknown as Mock)).toHaveBeenCalledWith({ success: true });
-  });
-
-  it('handles errors and presents failure result', async () => {
-    mediaRepo.findById.mockRejectedValue(new Error('DB error'));
-
-    await useCase.execute({ mediaId: 'media-1' }, presenter);
-
-    expect((logger.error as unknown as Mock)).toHaveBeenCalled();
-    expect((presenter.present as unknown as Mock)).toHaveBeenCalledWith({
-      success: false,
-      errorMessage: 'Internal error occurred while deleting media',
+    expect(output.present).toHaveBeenCalledWith({
+      mediaId: 'media-1',
+      deleted: true,
     });
   });
+
+  it('handles repository errors by returning REPOSITORY_ERROR', async () => {
+    mediaRepo.findById.mockRejectedValue(new Error('DB error'));
+
+    const input: DeleteMediaInput = { mediaId: 'media-1' };
+    const result = await useCase.execute(input);
+
+    expect((logger.error as unknown as Mock)).toHaveBeenCalled();
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr() as ApplicationErrorCode<
+      DeleteMediaErrorCode,
+      { message: string }
+    >;
+    expect(err.code).toBe('REPOSITORY_ERROR');
+    expect(output.present).not.toHaveBeenCalled();
+  });
 });

core/media/application/use-cases/DeleteMediaUseCase.ts

@@ -6,71 +6,73 @@
 
 import type { IMediaRepository } from '../../domain/repositories/IMediaRepository';
 import type { MediaStoragePort } from '../ports/MediaStoragePort';
-import type { Logger } from '@core/shared/application';
-import type { IDeleteMediaPresenter } from '../presenters/IDeleteMediaPresenter';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 
 export interface DeleteMediaInput {
   mediaId: string;
 }
 
 export interface DeleteMediaResult {
-  success: boolean;
-  errorMessage?: string;
+  mediaId: string;
+  deleted: boolean;
 }
 
-export interface IDeleteMediaPresenter {
-  present(result: DeleteMediaResult): void;
-}
+export type DeleteMediaErrorCode = 'MEDIA_NOT_FOUND' | 'REPOSITORY_ERROR';
+
+export type DeleteMediaApplicationError = ApplicationErrorCode<
+  DeleteMediaErrorCode,
+  { message: string }
+>;
 
 export class DeleteMediaUseCase {
   constructor(
     private readonly mediaRepo: IMediaRepository,
     private readonly mediaStorage: MediaStoragePort,
+    private readonly output: UseCaseOutputPort<DeleteMediaResult>,
     private readonly logger: Logger,
   ) {}
 
-  async execute(
-    input: DeleteMediaInput,
-    presenter: IDeleteMediaPresenter,
-  ): Promise<void> {
-    try {
-      this.logger.info('[DeleteMediaUseCase] Deleting media', {
-        mediaId: input.mediaId,
-      });
+  async execute(input: DeleteMediaInput): Promise<Result<void, DeleteMediaApplicationError>> {
+    this.logger.info('[DeleteMediaUseCase] Deleting media', {
+      mediaId: input.mediaId,
+    });
 
+    try {
       const media = await this.mediaRepo.findById(input.mediaId);
 
       if (!media) {
-        presenter.present({
-          success: false,
-          errorMessage: 'Media not found',
+        return Result.err({
+          code: 'MEDIA_NOT_FOUND',
+          details: { message: 'Media not found' },
         });
-        return;
       }
 
-      // Delete from storage
       await this.mediaStorage.deleteMedia(media.url.value);
-
-      // Delete from repository
       await this.mediaRepo.delete(input.mediaId);
 
-      presenter.present({
-        success: true,
+      this.output.present({
+        mediaId: input.mediaId,
+        deleted: true,
       });
 
       this.logger.info('[DeleteMediaUseCase] Media deleted successfully', {
         mediaId: input.mediaId,
       });
 
+      return Result.ok(undefined);
     } catch (error) {
+      const err = error instanceof Error ? error : new Error(String(error));
+
       this.logger.error('[DeleteMediaUseCase] Error deleting media', {
-        error: error instanceof Error ? error.message : 'Unknown error',
+        error: err.message,
         mediaId: input.mediaId,
       });
 
-      presenter.present({
-        success: false,
-        errorMessage: 'Internal error occurred while deleting media',
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message ?? 'Unexpected repository error' },
       });
     }
   }

core/media/application/use-cases/GetAvatarUseCase.test.ts

@@ -1,13 +1,19 @@
 import { describe, it, expect, vi, type Mock } from 'vitest';
-import { GetAvatarUseCase } from './GetAvatarUseCase';
+import {
+  GetAvatarUseCase,
+  type GetAvatarInput,
+  type GetAvatarResult,
+  type GetAvatarErrorCode,
+} from './GetAvatarUseCase';
 import type { IAvatarRepository } from '../../domain/repositories/IAvatarRepository';
-import type { IGetAvatarPresenter } from '../presenters/IGetAvatarPresenter';
-import type { Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import { Avatar } from '../../domain/entities/Avatar';
-import { MediaUrl } from '../../domain/value-objects/MediaUrl';
 
-interface TestPresenter extends IGetAvatarPresenter {
-  result?: any;
+interface TestOutputPort extends UseCaseOutputPort<GetAvatarResult> {
+  present: Mock;
+  result?: GetAvatarResult;
 }
 
 describe('GetAvatarUseCase', () => {
@@ -16,7 +22,7 @@ describe('GetAvatarUseCase', () => {
     save: Mock;
   };
   let logger: Logger;
-  let presenter: TestPresenter;
+  let output: TestOutputPort;
   let useCase: GetAvatarUseCase;
 
   beforeEach(() => {
@@ -32,44 +38,51 @@ describe('GetAvatarUseCase', () => {
       error: vi.fn(),
     } as unknown as Logger;
 
-    presenter = {
-      present: vi.fn((result) => {
-        presenter.result = result;
+    output = {
+      present: vi.fn((result: GetAvatarResult) => {
+        output.result = result;
       }),
-    } as unknown as TestPresenter;
+    } as unknown as TestOutputPort;
 
     useCase = new GetAvatarUseCase(
       avatarRepo as unknown as IAvatarRepository,
+      output,
       logger,
     );
   });
 
-  it('presents error when no avatar exists for driver', async () => {
+  it('returns AVATAR_NOT_FOUND when no avatar exists for driver', async () => {
     avatarRepo.findActiveByDriverId.mockResolvedValue(null);
 
-    await useCase.execute({ driverId: 'driver-1' }, presenter);
+    const input: GetAvatarInput = { driverId: 'driver-1' };
+    const result = await useCase.execute(input);
 
     expect(avatarRepo.findActiveByDriverId).toHaveBeenCalledWith('driver-1');
-    expect((presenter.present as unknown as Mock)).toHaveBeenCalledWith({
-      success: false,
-      errorMessage: 'Avatar not found',
-    });
+    expect(result).toBeInstanceOf(Result);
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr() as ApplicationErrorCode<
+      GetAvatarErrorCode,
+      { message: string }
+    >;
+    expect(err.code).toBe('AVATAR_NOT_FOUND');
+    expect(output.present).not.toHaveBeenCalled();
   });
 
   it('presents avatar details when avatar exists', async () => {
     const avatar = Avatar.create({
       id: 'avatar-1',
       driverId: 'driver-1',
-      mediaUrl: MediaUrl.create('https://example.com/avatar.png'),
+      mediaUrl: 'https://example.com/avatar.png',
     });
 
     avatarRepo.findActiveByDriverId.mockResolvedValue(avatar);
 
-    await useCase.execute({ driverId: 'driver-1' }, presenter);
+    const input: GetAvatarInput = { driverId: 'driver-1' };
+    const result = await useCase.execute(input);
 
+    expect(result.isOk()).toBe(true);
     expect(avatarRepo.findActiveByDriverId).toHaveBeenCalledWith('driver-1');
-    expect((presenter.present as unknown as Mock)).toHaveBeenCalledWith({
-      success: true,
+    expect(output.present).toHaveBeenCalledWith({
       avatar: {
         id: avatar.id,
         driverId: avatar.driverId,
@@ -79,15 +92,19 @@ describe('GetAvatarUseCase', () => {
     });
   });
 
-  it('handles errors by logging and presenting failure', async () => {
+  it('handles repository errors by returning REPOSITORY_ERROR', async () => {
     avatarRepo.findActiveByDriverId.mockRejectedValue(new Error('DB error'));
 
-    await useCase.execute({ driverId: 'driver-1' }, presenter);
+    const input: GetAvatarInput = { driverId: 'driver-1' };
+    const result = await useCase.execute(input);
 
     expect((logger.error as unknown as Mock)).toHaveBeenCalled();
-    expect((presenter.present as unknown as Mock)).toHaveBeenCalledWith({
-      success: false,
-      errorMessage: 'Internal error occurred while retrieving avatar',
-    });
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr() as ApplicationErrorCode<
+      GetAvatarErrorCode,
+      { message: string }
+    >;
+    expect(err.code).toBe('REPOSITORY_ERROR');
+    expect(output.present).not.toHaveBeenCalled();
   });
 });

core/media/application/use-cases/GetAvatarUseCase.ts

@@ -5,55 +5,53 @@
  */
 
 import type { IAvatarRepository } from '../../domain/repositories/IAvatarRepository';
-import type { Logger } from '@core/shared/application';
-import type { IGetAvatarPresenter } from '../presenters/IGetAvatarPresenter';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 
 export interface GetAvatarInput {
   driverId: string;
 }
 
 export interface GetAvatarResult {
-  success: boolean;
-  avatar?: {
+  avatar: {
     id: string;
     driverId: string;
     mediaUrl: string;
     selectedAt: Date;
   };
-  errorMessage?: string;
 }
 
-export interface IGetAvatarPresenter {
-  present(result: GetAvatarResult): void;
-}
+export type GetAvatarErrorCode = 'AVATAR_NOT_FOUND' | 'REPOSITORY_ERROR';
+
+export type GetAvatarApplicationError = ApplicationErrorCode<
+  GetAvatarErrorCode,
+  { message: string }
+>;
 
 export class GetAvatarUseCase {
   constructor(
     private readonly avatarRepo: IAvatarRepository,
+    private readonly output: UseCaseOutputPort<GetAvatarResult>,
     private readonly logger: Logger,
   ) {}
 
-  async execute(
-    input: GetAvatarInput,
-    presenter: IGetAvatarPresenter,
-  ): Promise<void> {
-    try {
-      this.logger.info('[GetAvatarUseCase] Getting avatar', {
-        driverId: input.driverId,
-      });
+  async execute(input: GetAvatarInput): Promise<Result<void, GetAvatarApplicationError>> {
+    this.logger.info('[GetAvatarUseCase] Getting avatar', {
+      driverId: input.driverId,
+    });
 
+    try {
       const avatar = await this.avatarRepo.findActiveByDriverId(input.driverId);
 
       if (!avatar) {
-        presenter.present({
-          success: false,
-          errorMessage: 'Avatar not found',
+        return Result.err({
+          code: 'AVATAR_NOT_FOUND',
+          details: { message: 'Avatar not found' },
         });
-        return;
       }
 
-      presenter.present({
-        success: true,
+      this.output.present({
         avatar: {
           id: avatar.id,
           driverId: avatar.driverId,
@@ -62,15 +60,17 @@ export class GetAvatarUseCase {
         },
       });
 
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error('[GetAvatarUseCase] Error getting avatar', {
-        error: error instanceof Error ? error.message : 'Unknown error',
+      const err = error instanceof Error ? error : new Error(String(error));
+
+      this.logger.error('[GetAvatarUseCase] Error getting avatar', err, {
         driverId: input.driverId,
       });
 
-      presenter.present({
-        success: false,
-        errorMessage: 'Internal error occurred while retrieving avatar',
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message ?? 'Unexpected repository error' },
       });
     }
   }

core/media/application/use-cases/GetMediaUseCase.test.ts

@@ -1,13 +1,20 @@
 import { describe, it, expect, vi, type Mock } from 'vitest';
-import { GetMediaUseCase } from './GetMediaUseCase';
+import {
+  GetMediaUseCase,
+  type GetMediaInput,
+  type GetMediaResult,
+  type GetMediaErrorCode,
+} from './GetMediaUseCase';
 import type { IMediaRepository } from '../../domain/repositories/IMediaRepository';
-import type { IGetMediaPresenter } from '../presenters/IGetMediaPresenter';
-import type { Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import { Media } from '../../domain/entities/Media';
 import { MediaUrl } from '../../domain/value-objects/MediaUrl';
 
-interface TestPresenter extends IGetMediaPresenter {
-  result?: any;
+interface TestOutputPort extends UseCaseOutputPort<GetMediaResult> {
+  present: Mock;
+  result?: GetMediaResult;
 }
 
 describe('GetMediaUseCase', () => {
@@ -15,7 +22,7 @@ describe('GetMediaUseCase', () => {
     findById: Mock;
   };
   let logger: Logger;
-  let presenter: TestPresenter;
+  let output: TestOutputPort;
   let useCase: GetMediaUseCase;
 
   beforeEach(() => {
@@ -30,28 +37,31 @@ describe('GetMediaUseCase', () => {
       error: vi.fn(),
     } as unknown as Logger;
 
-    presenter = {
-      present: vi.fn((result) => {
-        presenter.result = result;
+    output = {
+      present: vi.fn((result: GetMediaResult) => {
+        output.result = result;
       }),
-    } as unknown as TestPresenter;
+    } as unknown as TestOutputPort;
 
     useCase = new GetMediaUseCase(
       mediaRepo as unknown as IMediaRepository,
+      output,
       logger,
     );
   });
 
-  it('presents error when media is not found', async () => {
+  it('returns MEDIA_NOT_FOUND when media is not found', async () => {
     mediaRepo.findById.mockResolvedValue(null);
 
-    await useCase.execute({ mediaId: 'missing' }, presenter);
+    const input: GetMediaInput = { mediaId: 'missing' };
+    const result = await useCase.execute(input);
 
     expect(mediaRepo.findById).toHaveBeenCalledWith('missing');
-    expect((presenter.present as unknown as Mock)).toHaveBeenCalledWith({
-      success: false,
-      errorMessage: 'Media not found',
-    });
+    expect(result).toBeInstanceOf(Result);
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr() as ApplicationErrorCode<GetMediaErrorCode, { message: string }>;
+    expect(err.code).toBe('MEDIA_NOT_FOUND');
+    expect(output.present).not.toHaveBeenCalled();
   });
 
   it('presents media details when media exists', async () => {
@@ -68,11 +78,12 @@ describe('GetMediaUseCase', () => {
 
     mediaRepo.findById.mockResolvedValue(media);
 
-    await useCase.execute({ mediaId: 'media-1' }, presenter);
+    const input: GetMediaInput = { mediaId: 'media-1' };
+    const result = await useCase.execute(input);
 
+    expect(result.isOk()).toBe(true);
     expect(mediaRepo.findById).toHaveBeenCalledWith('media-1');
-    expect((presenter.present as unknown as Mock)).toHaveBeenCalledWith({
-      success: true,
+    expect(output.present).toHaveBeenCalledWith({
       media: {
         id: media.id,
         filename: media.filename,
@@ -88,15 +99,15 @@ describe('GetMediaUseCase', () => {
     });
   });
 
-  it('handles errors by logging and presenting failure', async () => {
+  it('handles repository errors by returning REPOSITORY_ERROR', async () => {
     mediaRepo.findById.mockRejectedValue(new Error('DB error'));
 
-    await useCase.execute({ mediaId: 'media-1' }, presenter);
+    const input: GetMediaInput = { mediaId: 'media-1' };
+    const result = await useCase.execute(input);
 
     expect((logger.error as unknown as Mock)).toHaveBeenCalled();
-    expect((presenter.present as unknown as Mock)).toHaveBeenCalledWith({
-      success: false,
-      errorMessage: 'Internal error occurred while retrieving media',
-    });
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr() as ApplicationErrorCode<GetMediaErrorCode, { message: string }>;
+    expect(err.code).toBe('REPOSITORY_ERROR');
   });
 });

core/media/application/use-cases/GetMediaUseCase.ts

@@ -5,16 +5,16 @@
  */
 
 import type { IMediaRepository } from '../../domain/repositories/IMediaRepository';
-import type { Logger } from '@core/shared/application';
-import type { IGetMediaPresenter } from '../presenters/IGetMediaPresenter';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 
 export interface GetMediaInput {
   mediaId: string;
 }
 
 export interface GetMediaResult {
-  success: boolean;
-  media?: {
+  media: {
     id: string;
     filename: string;
     originalName: string;
@@ -26,40 +26,35 @@ export interface GetMediaResult {
     uploadedAt: Date;
     metadata?: Record<string, any>;
   };
-  errorMessage?: string;
 }
 
-export interface IGetMediaPresenter {
-  present(result: GetMediaResult): void;
-}
+export type GetMediaErrorCode = 'MEDIA_NOT_FOUND' | 'REPOSITORY_ERROR';
 
 export class GetMediaUseCase {
   constructor(
     private readonly mediaRepo: IMediaRepository,
+    private readonly output: UseCaseOutputPort<GetMediaResult>,
     private readonly logger: Logger,
   ) {}
 
   async execute(
     input: GetMediaInput,
-    presenter: IGetMediaPresenter,
-  ): Promise<void> {
-    try {
-      this.logger.info('[GetMediaUseCase] Getting media', {
-        mediaId: input.mediaId,
-      });
+  ): Promise<Result<void, ApplicationErrorCode<GetMediaErrorCode, { message: string }>>> {
+    this.logger.info('[GetMediaUseCase] Getting media', {
+      mediaId: input.mediaId,
+    });
 
+   try {
       const media = await this.mediaRepo.findById(input.mediaId);
 
       if (!media) {
-        presenter.present({
-          success: false,
-          errorMessage: 'Media not found',
+        return Result.err({
+          code: 'MEDIA_NOT_FOUND',
+          details: { message: 'Media not found' },
         });
-        return;
       }
 
-      presenter.present({
-        success: true,
+      this.output.present({
         media: {
           id: media.id,
           filename: media.filename,
@@ -74,15 +69,16 @@ export class GetMediaUseCase {
         },
       });
 
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error('[GetMediaUseCase] Error getting media', {
-        error: error instanceof Error ? error.message : 'Unknown error',
+      const err = error instanceof Error ? error : new Error(String(error));
+      this.logger.error('[GetMediaUseCase] Error getting media', err, {
         mediaId: input.mediaId,
       });
 
-      presenter.present({
-        success: false,
-        errorMessage: 'Internal error occurred while retrieving media',
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
       });
     }
   }

core/media/application/use-cases/RequestAvatarGenerationUseCase.ts

@@ -8,10 +8,11 @@ import { v4 as uuidv4 } from 'uuid';
 import type { IAvatarGenerationRepository } from '../../domain/repositories/IAvatarGenerationRepository';
 import type { FaceValidationPort } from '../ports/FaceValidationPort';
 import type { AvatarGenerationPort } from '../ports/AvatarGenerationPort';
-import type { Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
 import { AvatarGenerationRequest } from '../../domain/entities/AvatarGenerationRequest';
-import type { IRequestAvatarGenerationPresenter } from '../presenters/IRequestAvatarGenerationPresenter';
 import type { RacingSuitColor } from '../../domain/types/AvatarGenerationRequest';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 
 export interface RequestAvatarGenerationInput {
   userId: string;
@@ -20,63 +21,68 @@ export interface RequestAvatarGenerationInput {
   style?: 'realistic' | 'cartoon' | 'pixel-art';
 }
 
+export interface RequestAvatarGenerationResult {
+  requestId: string;
+  status: 'validating' | 'generating' | 'completed';
+  avatarUrls?: string[];
+}
+
+export type RequestAvatarGenerationErrorCode =
+  | 'FACE_VALIDATION_FAILED'
+  | 'GENERATION_FAILED'
+  | 'REPOSITORY_ERROR';
+
+export type RequestAvatarGenerationApplicationError = ApplicationErrorCode<
+  RequestAvatarGenerationErrorCode,
+  { message: string }
+>;
+
 export class RequestAvatarGenerationUseCase {
   constructor(
     private readonly avatarRepo: IAvatarGenerationRepository,
     private readonly faceValidation: FaceValidationPort,
     private readonly avatarGeneration: AvatarGenerationPort,
+    private readonly output: UseCaseOutputPort<RequestAvatarGenerationResult>,
     private readonly logger: Logger,
   ) {}
 
   async execute(
     input: RequestAvatarGenerationInput,
-    presenter: IRequestAvatarGenerationPresenter,
-  ): Promise<void> {
-    try {
-      this.logger.info('[RequestAvatarGenerationUseCase] Starting avatar generation request', {
-        userId: input.userId,
-        suitColor: input.suitColor,
-      });
+  ): Promise<Result<void, RequestAvatarGenerationApplicationError>> {
+    this.logger.info('[RequestAvatarGenerationUseCase] Starting avatar generation request', {
+      userId: input.userId,
+      suitColor: input.suitColor,
+    });
 
-      // Create the avatar generation request entity
+    try {
       const requestId = uuidv4();
       const request = AvatarGenerationRequest.create({
         id: requestId,
         userId: input.userId,
-        facePhotoUrl: input.facePhotoData, // Assuming facePhotoData is a URL or base64
+        facePhotoUrl: input.facePhotoData,
         suitColor: input.suitColor,
         style: input.style,
       });
 
-      // Save initial request
       await this.avatarRepo.save(request);
 
-      // Present initial status
-      presenter.present({
-        requestId,
-        status: 'validating',
-      });
-
-      // Validate face photo
       request.markAsValidating();
       await this.avatarRepo.save(request);
 
       const validationResult = await this.faceValidation.validateFacePhoto(input.facePhotoData);
 
       if (!validationResult.isValid || !validationResult.hasFace || validationResult.faceCount !== 1) {
-        const errorMessage = validationResult.errorMessage || 'Invalid face photo: must contain exactly one face';
+        const errorMessage =
+          validationResult.errorMessage || 'Invalid face photo: must contain exactly one face';
         request.fail(errorMessage);
         await this.avatarRepo.save(request);
 
-        presenter.present({
-          requestId,
-          status: 'failed',
-          errorMessage,
+        return Result.err({
+          code: 'FACE_VALIDATION_FAILED',
+          details: { message: errorMessage },
         });
-        return;
       }
 
-      // Generate avatars
       request.markAsGenerating();
       await this.avatarRepo.save(request);
 
@@ -85,7 +91,7 @@ export class RequestAvatarGenerationUseCase {
         prompt: request.buildPrompt(),
         suitColor: input.suitColor,
         style: input.style || 'realistic',
-        count: 3, // Generate 3 avatar options
+        count: 3,
       };
 
       const generationResult = await this.avatarGeneration.generateAvatars(generationOptions);
@@ -95,20 +101,17 @@ export class RequestAvatarGenerationUseCase {
         request.fail(errorMessage);
         await this.avatarRepo.save(request);
 
-        presenter.present({
-          requestId,
-          status: 'failed',
-          errorMessage,
+        return Result.err({
+          code: 'GENERATION_FAILED',
+          details: { message: errorMessage },
         });
-        return;
       }
 
-      // Complete the request
       const avatarUrls = generationResult.avatars.map(avatar => avatar.url);
       request.completeWithAvatars(avatarUrls);
       await this.avatarRepo.save(request);
 
-      presenter.present({
+      this.output.present({
         requestId,
         status: 'completed',
         avatarUrls,
@@ -120,16 +123,17 @@ export class RequestAvatarGenerationUseCase {
         avatarCount: avatarUrls.length,
       });
 
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error('[RequestAvatarGenerationUseCase] Error during avatar generation', {
-        error: error instanceof Error ? error.message : 'Unknown error',
+      const err = error instanceof Error ? error : new Error(String(error));
+
+      this.logger.error('[RequestAvatarGenerationUseCase] Error during avatar generation', err, {
         userId: input.userId,
       });
 
-      presenter.present({
-        requestId: uuidv4(), // Fallback ID
-        status: 'failed',
-        errorMessage: 'Internal error occurred during avatar generation',
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message ?? 'Internal error occurred during avatar generation' },
       });
     }
   }

core/media/application/use-cases/SelectAvatarUseCase.ts

@@ -5,8 +5,9 @@
  */
 
 import type { IAvatarGenerationRepository } from '../../domain/repositories/IAvatarGenerationRepository';
-import type { Logger } from '@core/shared/application';
-import type { ISelectAvatarPresenter } from '../presenters/ISelectAvatarPresenter';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 
 export interface SelectAvatarInput {
   requestId: string;
@@ -14,47 +15,48 @@ export interface SelectAvatarInput {
 }
 
 export interface SelectAvatarResult {
-  success: boolean;
-  selectedAvatarUrl?: string;
-  errorMessage?: string;
+  requestId: string;
+  selectedAvatarUrl: string;
 }
 
-export interface ISelectAvatarPresenter {
-  present(result: SelectAvatarResult): void;
-}
+export type SelectAvatarErrorCode =
+  | 'REQUEST_NOT_FOUND'
+  | 'REQUEST_NOT_COMPLETED'
+  | 'REPOSITORY_ERROR';
+
+export type SelectAvatarApplicationError = ApplicationErrorCode<
+  SelectAvatarErrorCode,
+  { message: string }
+>;
 
 export class SelectAvatarUseCase {
   constructor(
     private readonly avatarRepo: IAvatarGenerationRepository,
+    private readonly output: UseCaseOutputPort<SelectAvatarResult>,
     private readonly logger: Logger,
   ) {}
 
-  async execute(
-    input: SelectAvatarInput,
-    presenter: ISelectAvatarPresenter,
-  ): Promise<void> {
-    try {
-      this.logger.info('[SelectAvatarUseCase] Selecting avatar', {
-        requestId: input.requestId,
-        selectedIndex: input.selectedIndex,
-      });
+  async execute(input: SelectAvatarInput): Promise<Result<void, SelectAvatarApplicationError>> {
+    this.logger.info('[SelectAvatarUseCase] Selecting avatar', {
+      requestId: input.requestId,
+      selectedIndex: input.selectedIndex,
+    });
 
+    try {
       const request = await this.avatarRepo.findById(input.requestId);
 
       if (!request) {
-        presenter.present({
-          success: false,
-          errorMessage: 'Avatar generation request not found',
+        return Result.err({
+          code: 'REQUEST_NOT_FOUND',
+          details: { message: 'Avatar generation request not found' },
         });
-        return;
       }
 
       if (request.status !== 'completed') {
-        presenter.present({
-          success: false,
-          errorMessage: 'Avatar generation is not completed yet',
+        return Result.err({
+          code: 'REQUEST_NOT_COMPLETED',
+          details: { message: 'Avatar generation is not completed yet' },
         });
-        return;
       }
 
       request.selectAvatar(input.selectedIndex);
@@ -62,8 +64,8 @@ export class SelectAvatarUseCase {
 
       const selectedAvatarUrl = request.selectedAvatarUrl;
 
-      presenter.present({
-        success: true,
+      this.output.present({
+        requestId: input.requestId,
         selectedAvatarUrl,
       });
 
@@ -72,15 +74,17 @@ export class SelectAvatarUseCase {
         selectedAvatarUrl,
       });
 
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error('[SelectAvatarUseCase] Error selecting avatar', {
-        error: error instanceof Error ? error.message : 'Unknown error',
+      const err = error instanceof Error ? error : new Error(String(error));
+
+      this.logger.error('[SelectAvatarUseCase] Error selecting avatar', err, {
         requestId: input.requestId,
       });
 
-      presenter.present({
-        success: false,
-        errorMessage: 'Internal error occurred while selecting avatar',
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message ?? 'Unexpected repository error' },
       });
     }
   }

core/media/application/use-cases/UpdateAvatarUseCase.ts

@@ -4,11 +4,12 @@
  * Handles the business logic for updating a driver's avatar.
  */
 
-import type { IAvatarRepository } from '../../domain/repositories/IAvatarRepository';
-import type { Logger } from '@core/shared/application';
-import { Avatar } from '../../domain/entities/Avatar';
-import type { IUpdateAvatarPresenter } from '../presenters/IUpdateAvatarPresenter';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import { v4 as uuidv4 } from 'uuid';
+import { Avatar } from '../../domain/entities/Avatar';
+import type { IAvatarRepository } from '../../domain/repositories/IAvatarRepository';
 
 export interface UpdateAvatarInput {
   driverId: string;
@@ -16,39 +17,38 @@ export interface UpdateAvatarInput {
 }
 
 export interface UpdateAvatarResult {
-  success: boolean;
-  errorMessage?: string;
+  avatarId: string;
+  driverId: string;
 }
 
-export interface IUpdateAvatarPresenter {
-  present(result: UpdateAvatarResult): void;
-}
+export type UpdateAvatarErrorCode = 'REPOSITORY_ERROR';
+
+export type UpdateAvatarApplicationError = ApplicationErrorCode<
+  UpdateAvatarErrorCode,
+  { message: string }
+>;
 
 export class UpdateAvatarUseCase {
   constructor(
     private readonly avatarRepo: IAvatarRepository,
+    private readonly output: UseCaseOutputPort<UpdateAvatarResult>,
     private readonly logger: Logger,
   ) {}
 
-  async execute(
-    input: UpdateAvatarInput,
-    presenter: IUpdateAvatarPresenter,
-  ): Promise<void> {
-    try {
-      this.logger.info('[UpdateAvatarUseCase] Updating avatar', {
-        driverId: input.driverId,
-        mediaUrl: input.mediaUrl,
-      });
+  async execute(input: UpdateAvatarInput): Promise<Result<void, UpdateAvatarApplicationError>> {
+    this.logger.info('[UpdateAvatarUseCase] Updating avatar', {
+      driverId: input.driverId,
+      mediaUrl: input.mediaUrl,
+    });
 
-      // Deactivate current active avatar
+    try {
       const currentAvatar = await this.avatarRepo.findActiveByDriverId(input.driverId);
       if (currentAvatar) {
         currentAvatar.deactivate();
         await this.avatarRepo.save(currentAvatar);
       }
 
-      // Create new avatar
-      const avatarId = uuidv4();
+      const avatarId = uuidv4(); // TODO this ID should be a value object
       const newAvatar = Avatar.create({
         id: avatarId,
         driverId: input.driverId,
@@ -57,8 +57,9 @@ export class UpdateAvatarUseCase {
 
       await this.avatarRepo.save(newAvatar);
 
-      presenter.present({
-        success: true,
+      this.output.present({
+        avatarId,
+        driverId: input.driverId,
       });
 
       this.logger.info('[UpdateAvatarUseCase] Avatar updated successfully', {
@@ -66,15 +67,17 @@ export class UpdateAvatarUseCase {
         avatarId,
       });
 
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error('[UpdateAvatarUseCase] Error updating avatar', {
-        error: error instanceof Error ? error.message : 'Unknown error',
+      const err = error instanceof Error ? error : new Error(String(error));
+
+      this.logger.error('[UpdateAvatarUseCase] Error updating avatar', err, {
         driverId: input.driverId,
       });
 
-      presenter.present({
-        success: false,
-        errorMessage: 'Internal error occurred while updating avatar',
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message ?? 'Internal error occurred while updating avatar' },
       });
     }
   }

core/media/application/use-cases/UploadMediaUseCase.ts

@@ -6,9 +6,10 @@
 
 import type { IMediaRepository } from '../../domain/repositories/IMediaRepository';
 import type { MediaStoragePort } from '../ports/MediaStoragePort';
-import type { Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import { Media } from '../../domain/entities/Media';
-import type { IUploadMediaPresenter } from '../presenters/IUploadMediaPresenter';
 import { v4 as uuidv4 } from 'uuid';
 
 export interface UploadMediaInput {
@@ -18,34 +19,32 @@ export interface UploadMediaInput {
 }
 
 export interface UploadMediaResult {
-  success: boolean;
-  mediaId?: string;
-  url?: string;
-  errorMessage?: string;
+  mediaId: string;
+  url: string | undefined;
 }
 
-export interface IUploadMediaPresenter {
-  present(result: UploadMediaResult): void;
-}
+export type UploadMediaErrorCode =
+  | 'UPLOAD_FAILED'
+  | 'REPOSITORY_ERROR';
 
 export class UploadMediaUseCase {
   constructor(
     private readonly mediaRepo: IMediaRepository,
     private readonly mediaStorage: MediaStoragePort,
+    private readonly output: UseCaseOutputPort<UploadMediaResult>,
     private readonly logger: Logger,
   ) {}
 
   async execute(
     input: UploadMediaInput,
-    presenter: IUploadMediaPresenter,
-  ): Promise<void> {
-    try {
-      this.logger.info('[UploadMediaUseCase] Starting media upload', {
-        filename: input.file.originalname,
-        size: input.file.size,
-        uploadedBy: input.uploadedBy,
-      });
+  ): Promise<Result<void, ApplicationErrorCode<UploadMediaErrorCode, { message: string }>>> {
+    this.logger.info('[UploadMediaUseCase] Starting media upload', {
+      filename: input.file.originalname,
+      size: input.file.size,
+      uploadedBy: input.uploadedBy,
+    });
 
+    try {
       // Upload file to storage service
       const uploadResult = await this.mediaStorage.uploadMedia(input.file.buffer, {
         filename: input.file.originalname,
@@ -54,11 +53,13 @@ export class UploadMediaUseCase {
       });
 
       if (!uploadResult.success) {
-        presenter.present({
-          success: false,
-          errorMessage: uploadResult.errorMessage || 'Failed to upload media',
+        return Result.err({
+          code: 'UPLOAD_FAILED',
+          details: {
+            message:
+              uploadResult.errorMessage ?? 'Failed to upload media',
+          },
         });
-        return;
       }
 
       // Determine media type
@@ -85,8 +86,7 @@ export class UploadMediaUseCase {
       // Save to repository
       await this.mediaRepo.save(media);
 
-      presenter.present({
-        success: true,
+      this.output.present({
         mediaId,
         url: uploadResult.url,
       });
@@ -96,15 +96,17 @@ export class UploadMediaUseCase {
         url: uploadResult.url,
       });
 
+      return Result.ok(undefined);
     } catch (error) {
+      const err = error instanceof Error ? error : new Error(String(error));
       this.logger.error('[UploadMediaUseCase] Error uploading media', {
-        error: error instanceof Error ? error.message : 'Unknown error',
+        error: err.message,
         filename: input.file.originalname,
       });
 
-      presenter.present({
-        success: false,
-        errorMessage: 'Internal error occurred during media upload',
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
       });
     }
   }

core/notifications/application/use-cases/GetUnreadNotificationsUseCase.test.ts

@@ -1,16 +1,27 @@
 import { describe, it, expect, vi, type Mock } from 'vitest';
-import { GetUnreadNotificationsUseCase } from './GetUnreadNotificationsUseCase';
+import {
+  GetUnreadNotificationsUseCase,
+  type GetUnreadNotificationsInput,
+  type GetUnreadNotificationsResult,
+} from './GetUnreadNotificationsUseCase';
 import type { INotificationRepository } from '../../domain/repositories/INotificationRepository';
-import type { Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import { Notification } from '../../domain/entities/Notification';
 
 interface NotificationRepositoryMock {
   findUnreadByRecipientId: Mock;
 }
 
+interface OutputPortMock extends UseCaseOutputPort<GetUnreadNotificationsResult> {
+  present: Mock;
+}
+
 describe('GetUnreadNotificationsUseCase', () => {
   let notificationRepository: NotificationRepositoryMock;
   let logger: Logger;
+  let output: OutputPortMock;
   let useCase: GetUnreadNotificationsUseCase;
 
   beforeEach(() => {
@@ -25,8 +36,13 @@ describe('GetUnreadNotificationsUseCase', () => {
       error: vi.fn(),
     } as unknown as Logger;
 
+    output = {
+      present: vi.fn(),
+    } as unknown as OutputPortMock;
+
     useCase = new GetUnreadNotificationsUseCase(
       notificationRepository as unknown as INotificationRepository,
+      output,
       logger,
     );
   });
@@ -37,7 +53,7 @@ describe('GetUnreadNotificationsUseCase', () => {
       Notification.create({
         id: 'n1',
         recipientId,
-        type: 'info',
+        type: 'system_announcement',
         title: 'Test',
         body: 'Body',
         channel: 'in_app',
@@ -46,19 +62,33 @@ describe('GetUnreadNotificationsUseCase', () => {
 
     notificationRepository.findUnreadByRecipientId.mockResolvedValue(notifications);
 
-    const result = await useCase.execute(recipientId);
+    const input: GetUnreadNotificationsInput = { recipientId };
+
+    const result = await useCase.execute(input);
 
     expect(notificationRepository.findUnreadByRecipientId).toHaveBeenCalledWith(recipientId);
-    expect(result.notifications).toEqual(notifications);
-    expect(result.totalCount).toBe(1);
+    expect(result).toBeInstanceOf(Result);
+    expect(result.isOk()).toBe(true);
+    expect(output.present).toHaveBeenCalledWith({
+      notifications,
+      totalCount: 1,
+    });
   });
 
-  it('handles repository errors by logging and rethrowing', async () => {
+  it('handles repository errors by logging and returning error result', async () => {
     const recipientId = 'driver-1';
     const error = new Error('DB error');
     notificationRepository.findUnreadByRecipientId.mockRejectedValue(error);
 
-    await expect(useCase.execute(recipientId)).rejects.toThrow('DB error');
+    const input: GetUnreadNotificationsInput = { recipientId };
+
+    const result = await useCase.execute(input);
+
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr() as ApplicationErrorCode<'REPOSITORY_ERROR', { message: string }>;
+    expect(err.code).toBe('REPOSITORY_ERROR');
+    expect(err.details.message).toBe('DB error');
     expect((logger.error as unknown as Mock)).toHaveBeenCalled();
+    expect(output.present).not.toHaveBeenCalled();
   });
 });

core/notifications/application/use-cases/GetUnreadNotificationsUseCase.ts

@@ -1,41 +1,72 @@
 /**
  * Application Use Case: GetUnreadNotificationsUseCase
- * 
+ *
  * Retrieves unread notifications for a recipient.
  */
 
-import type { AsyncUseCase , Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import type { Notification } from '../../domain/entities/Notification';
 import type { INotificationRepository } from '../../domain/repositories/INotificationRepository';
 
-export interface UnreadNotificationsResult {
+export type GetUnreadNotificationsInput = {
+  recipientId: string;
+};
+
+export interface GetUnreadNotificationsResult {
   notifications: Notification[];
   totalCount: number;
 }
 
-export class GetUnreadNotificationsUseCase implements AsyncUseCase<string, UnreadNotificationsResult> {
+export type GetUnreadNotificationsErrorCode = 'REPOSITORY_ERROR';
+
+export class GetUnreadNotificationsUseCase {
   constructor(
     private readonly notificationRepository: INotificationRepository,
+    private readonly output: UseCaseOutputPort<GetUnreadNotificationsResult>,
     private readonly logger: Logger,
   ) {}
 
-  async execute(recipientId: string): Promise<UnreadNotificationsResult> {
-    this.logger.debug(`Attempting to retrieve unread notifications for recipient ID: ${recipientId}`);
+  async execute(
+    input: GetUnreadNotificationsInput,
+  ): Promise<Result<void, ApplicationErrorCode<GetUnreadNotificationsErrorCode, { message: string }>>> {
+    const { recipientId } = input;
+    this.logger.debug(
+      `Attempting to retrieve unread notifications for recipient ID: ${recipientId}`,
+    );
+
     try {
-      const notifications = await this.notificationRepository.findUnreadByRecipientId(recipientId);
-      this.logger.info(`Successfully retrieved ${notifications.length} unread notifications for recipient ID: ${recipientId}`);
-      
+      const notifications = await this.notificationRepository.findUnreadByRecipientId(
+        recipientId,
+      );
+      this.logger.info(
+        `Successfully retrieved ${notifications.length} unread notifications for recipient ID: ${recipientId}`,
+      );
+
       if (notifications.length === 0) {
         this.logger.warn(`No unread notifications found for recipient ID: ${recipientId}`);
       }
 
-      return {
+      this.output.present({
         notifications,
         totalCount: notifications.length,
-      };
+      });
+
+      return Result.ok<void, ApplicationErrorCode<GetUnreadNotificationsErrorCode, { message: string }>>(
+        undefined,
+      );
     } catch (error) {
-      this.logger.error(`Failed to retrieve unread notifications for recipient ID: ${recipientId}`, error instanceof Error ? error : new Error(String(error)));
-      throw error;
+      const err = error instanceof Error ? error : new Error(String(error));
+      this.logger.error(
+        `Failed to retrieve unread notifications for recipient ID: ${recipientId}`,
+        err,
+      );
+
+      return Result.err<void, ApplicationErrorCode<GetUnreadNotificationsErrorCode, { message: string }>>({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
+      });
     }
   }
 }

core/notifications/application/use-cases/MarkNotificationReadUseCase.test.ts

@@ -1,9 +1,14 @@
 import { describe, it, expect, vi, type Mock } from 'vitest';
-import { MarkNotificationReadUseCase } from './MarkNotificationReadUseCase';
+import {
+  MarkNotificationReadUseCase,
+  type MarkNotificationReadCommand,
+  type MarkNotificationReadResult,
+} from './MarkNotificationReadUseCase';
 import type { INotificationRepository } from '../../domain/repositories/INotificationRepository';
-import type { Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import { Notification } from '../../domain/entities/Notification';
-import { NotificationDomainError } from '../../domain/errors/NotificationDomainError';
 
 interface NotificationRepositoryMock {
   findById: Mock;
@@ -11,9 +16,14 @@ interface NotificationRepositoryMock {
   markAllAsReadByRecipientId: Mock;
 }
 
+interface OutputPortMock extends UseCaseOutputPort<MarkNotificationReadResult> {
+  present: Mock;
+}
+
 describe('MarkNotificationReadUseCase', () => {
   let notificationRepository: NotificationRepositoryMock;
   let logger: Logger;
+  let output: OutputPortMock;
   let useCase: MarkNotificationReadUseCase;
 
   beforeEach(() => {
@@ -30,27 +40,39 @@ describe('MarkNotificationReadUseCase', () => {
       error: vi.fn(),
     } as unknown as Logger;
 
+    output = {
+      present: vi.fn(),
+    } as unknown as OutputPortMock;
+
     useCase = new MarkNotificationReadUseCase(
       notificationRepository as unknown as INotificationRepository,
+      output,
       logger,
     );
   });
 
-  it('throws when notification is not found', async () => {
+  it('returns NOTIFICATION_NOT_FOUND when notification is not found', async () => {
     notificationRepository.findById.mockResolvedValue(null);
 
-    await expect(
-      useCase.execute({ notificationId: 'n1', recipientId: 'driver-1' }),
-    ).rejects.toThrow(NotificationDomainError);
+    const command: MarkNotificationReadCommand = {
+      notificationId: 'n1',
+      recipientId: 'driver-1',
+    };
 
-    expect((logger.warn as unknown as Mock)).toHaveBeenCalled();
+    const result = await useCase.execute(command);
+
+    expect(result).toBeInstanceOf(Result);
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr() as ApplicationErrorCode<'NOTIFICATION_NOT_FOUND', { message: string }>;
+    expect(err.code).toBe('NOTIFICATION_NOT_FOUND');
+    expect(output.present).not.toHaveBeenCalled();
   });
 
-  it('throws when recipientId does not match', async () => {
+  it('returns RECIPIENT_MISMATCH when recipientId does not match', async () => {
     const notification = Notification.create({
       id: 'n1',
       recipientId: 'driver-2',
-      type: 'info',
+      type: 'system_announcement',
       title: 'Test',
       body: 'Body',
       channel: 'in_app',
@@ -58,16 +80,24 @@ describe('MarkNotificationReadUseCase', () => {
 
     notificationRepository.findById.mockResolvedValue(notification);
 
-    await expect(
-      useCase.execute({ notificationId: 'n1', recipientId: 'driver-1' }),
-    ).rejects.toThrow(NotificationDomainError);
+    const command: MarkNotificationReadCommand = {
+      notificationId: 'n1',
+      recipientId: 'driver-1',
+    };
+
+    const result = await useCase.execute(command);
+
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr() as ApplicationErrorCode<'RECIPIENT_MISMATCH', { message: string }>;
+    expect(err.code).toBe('RECIPIENT_MISMATCH');
+    expect(output.present).not.toHaveBeenCalled();
   });
 
-  it('marks notification as read when unread', async () => {
+  it('marks notification as read when unread and presents result', async () => {
     const notification = Notification.create({
       id: 'n1',
       recipientId: 'driver-1',
-      type: 'info',
+      type: 'system_announcement',
       title: 'Test',
       body: 'Body',
       channel: 'in_app',
@@ -75,9 +105,19 @@ describe('MarkNotificationReadUseCase', () => {
 
     notificationRepository.findById.mockResolvedValue(notification);
 
-    await useCase.execute({ notificationId: 'n1', recipientId: 'driver-1' });
+    const command: MarkNotificationReadCommand = {
+      notificationId: 'n1',
+      recipientId: 'driver-1',
+    };
 
+    const result = await useCase.execute(command);
+
+    expect(result.isOk()).toBe(true);
     expect(notificationRepository.update).toHaveBeenCalled();
-    expect((logger.info as unknown as Mock)).toHaveBeenCalled();
+    expect(output.present).toHaveBeenCalledWith({
+      notificationId: 'n1',
+      recipientId: 'driver-1',
+      wasAlreadyRead: false,
+    });
   });
 });

core/notifications/application/use-cases/MarkNotificationReadUseCase.ts

@@ -4,7 +4,9 @@
  * Marks a notification as read.
  */
 
-import type { AsyncUseCase , Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import type { INotificationRepository } from '../../domain/repositories/INotificationRepository';
 import { NotificationDomainError } from '../../domain/errors/NotificationDomainError';
 
@@ -13,38 +15,86 @@ export interface MarkNotificationReadCommand {
   recipientId: string; // For validation
 }
 
-export class MarkNotificationReadUseCase implements AsyncUseCase<MarkNotificationReadCommand, void> {
+export interface MarkNotificationReadResult {
+  notificationId: string;
+  recipientId: string;
+  wasAlreadyRead: boolean;
+}
+
+export type MarkNotificationReadErrorCode =
+  | 'NOTIFICATION_NOT_FOUND'
+  | 'RECIPIENT_MISMATCH'
+  | 'REPOSITORY_ERROR';
+
+export class MarkNotificationReadUseCase {
   constructor(
     private readonly notificationRepository: INotificationRepository,
+    private readonly output: UseCaseOutputPort<MarkNotificationReadResult>,
     private readonly logger: Logger,
   ) {}
 
-  async execute(command: MarkNotificationReadCommand): Promise<void> {
-    this.logger.debug(`Attempting to mark notification ${command.notificationId} as read for recipient ${command.recipientId}`);
+  async execute(
+    command: MarkNotificationReadCommand,
+  ): Promise<Result<void, ApplicationErrorCode<MarkNotificationReadErrorCode, { message: string }>>> {
+    this.logger.debug(
+      `Attempting to mark notification ${command.notificationId} as read for recipient ${command.recipientId}`,
+    );
+
     try {
       const notification = await this.notificationRepository.findById(command.notificationId);
-      
+
       if (!notification) {
         this.logger.warn(`Notification not found for ID: ${command.notificationId}`);
-        throw new NotificationDomainError('Notification not found');
+        return Result.err({
+          code: 'NOTIFICATION_NOT_FOUND',
+          details: { message: 'Notification not found' },
+        });
       }
 
       if (notification.recipientId !== command.recipientId) {
-        this.logger.warn(`Unauthorized attempt to mark notification ${command.notificationId}. Recipient ID mismatch.`);
-        throw new NotificationDomainError('Cannot mark another user\'s notification as read');
+        this.logger.warn(
+          `Unauthorized attempt to mark notification ${command.notificationId}. Recipient ID mismatch.`,
+        );
+        return Result.err({
+          code: 'RECIPIENT_MISMATCH',
+          details: { message: "Cannot mark another user's notification as read" },
+        });
       }
 
       if (!notification.isUnread()) {
-        this.logger.info(`Notification ${command.notificationId} is already read. Skipping update.`);
-        return; // Already read, nothing to do
+        this.logger.info(
+          `Notification ${command.notificationId} is already read. Skipping update.`,
+        );
+        this.output.present({
+          notificationId: command.notificationId,
+          recipientId: command.recipientId,
+          wasAlreadyRead: true,
+        });
+        return Result.ok(undefined);
       }
 
       const updatedNotification = notification.markAsRead();
       await this.notificationRepository.update(updatedNotification);
-      this.logger.info(`Notification ${command.notificationId} successfully marked as read.`);
+      this.logger.info(
+        `Notification ${command.notificationId} successfully marked as read.`,
+      );
+
+      this.output.present({
+        notificationId: command.notificationId,
+        recipientId: command.recipientId,
+        wasAlreadyRead: false,
+      });
+
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error(`Failed to mark notification ${command.notificationId} as read: ${error instanceof Error ? error.message : String(error)}`);
-      throw error;
+      const err = error instanceof Error ? error : new Error(String(error));
+      this.logger.error(
+        `Failed to mark notification ${command.notificationId} as read: ${err.message}`,
+      );
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
+      });
     }
   }
 }
@@ -54,13 +104,36 @@ export class MarkNotificationReadUseCase implements AsyncUseCase<MarkNotificatio
  * 
  * Marks all notifications as read for a recipient.
  */
-export class MarkAllNotificationsReadUseCase implements AsyncUseCase<string, void> {
+export interface MarkAllNotificationsReadInput {
+  recipientId: string;
+}
+
+export interface MarkAllNotificationsReadResult {
+  recipientId: string;
+}
+
+export type MarkAllNotificationsReadErrorCode = 'REPOSITORY_ERROR';
+
+export class MarkAllNotificationsReadUseCase {
   constructor(
     private readonly notificationRepository: INotificationRepository,
+    private readonly output: UseCaseOutputPort<MarkAllNotificationsReadResult>,
   ) {}
 
-  async execute(recipientId: string): Promise<void> {
-    await this.notificationRepository.markAllAsReadByRecipientId(recipientId);
+  async execute(
+    input: MarkAllNotificationsReadInput,
+  ): Promise<Result<void, ApplicationErrorCode<MarkAllNotificationsReadErrorCode, { message: string }>>> {
+    try {
+      await this.notificationRepository.markAllAsReadByRecipientId(input.recipientId);
+      this.output.present({ recipientId: input.recipientId });
+      return Result.ok(undefined);
+    } catch (error) {
+      const err = error instanceof Error ? error : new Error(String(error));
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
+      });
+    }
   }
 }
 
@@ -74,27 +147,78 @@ export interface DismissNotificationCommand {
   recipientId: string;
 }
 
-export class DismissNotificationUseCase implements AsyncUseCase<DismissNotificationCommand, void> {
+export interface DismissNotificationResult {
+  notificationId: string;
+  recipientId: string;
+  wasAlreadyDismissed: boolean;
+}
+
+export type DismissNotificationErrorCode =
+  | 'NOTIFICATION_NOT_FOUND'
+  | 'RECIPIENT_MISMATCH'
+  | 'CANNOT_DISMISS_REQUIRING_RESPONSE'
+  | 'REPOSITORY_ERROR';
+
+export class DismissNotificationUseCase {
   constructor(
     private readonly notificationRepository: INotificationRepository,
+    private readonly output: UseCaseOutputPort<DismissNotificationResult>,
   ) {}
 
-  async execute(command: DismissNotificationCommand): Promise<void> {
-    const notification = await this.notificationRepository.findById(command.notificationId);
-    
-    if (!notification) {
-      throw new NotificationDomainError('Notification not found');
-    }
+  async execute(
+    command: DismissNotificationCommand,
+  ): Promise<Result<void, ApplicationErrorCode<DismissNotificationErrorCode, { message: string }>>> {
+    try {
+      const notification = await this.notificationRepository.findById(
+        command.notificationId,
+      );
 
-    if (notification.recipientId !== command.recipientId) {
-      throw new NotificationDomainError('Cannot dismiss another user\'s notification');
-    }
+      if (!notification) {
+        return Result.err({
+          code: 'NOTIFICATION_NOT_FOUND',
+          details: { message: 'Notification not found' },
+        });
+      }
 
-    if (notification.isDismissed()) {
-      return; // Already dismissed
-    }
+      if (notification.recipientId !== command.recipientId) {
+        return Result.err({
+          code: 'RECIPIENT_MISMATCH',
+          details: { message: "Cannot dismiss another user's notification" },
+        });
+      }
 
-    const updatedNotification = notification.dismiss();
-    await this.notificationRepository.update(updatedNotification);
+      if (notification.isDismissed()) {
+        this.output.present({
+          notificationId: command.notificationId,
+          recipientId: command.recipientId,
+          wasAlreadyDismissed: true,
+        });
+        return Result.ok(undefined);
+      }
+
+      if (!notification.canDismiss()) {
+        return Result.err({
+          code: 'CANNOT_DISMISS_REQUIRING_RESPONSE',
+          details: { message: 'Cannot dismiss notification that requires response' },
+        });
+      }
+
+      const updatedNotification = notification.dismiss();
+      await this.notificationRepository.update(updatedNotification);
+
+      this.output.present({
+        notificationId: command.notificationId,
+        recipientId: command.recipientId,
+        wasAlreadyDismissed: false,
+      });
+
+      return Result.ok(undefined);
+    } catch (error) {
+      const err = error instanceof Error ? error : new Error(String(error));
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
+      });
+    }
   }
 }

core/notifications/application/use-cases/NotificationPreferencesUseCases.test.ts

@@ -5,10 +5,22 @@ import {
   UpdateTypePreferenceUseCase,
   UpdateQuietHoursUseCase,
   SetDigestModeUseCase,
+  type GetNotificationPreferencesInput,
+  type GetNotificationPreferencesResult,
+  type UpdateChannelPreferenceCommand,
+  type UpdateChannelPreferenceResult,
+  type UpdateTypePreferenceCommand,
+  type UpdateTypePreferenceResult,
+  type UpdateQuietHoursCommand,
+  type UpdateQuietHoursResult,
+  type SetDigestModeCommand,
+  type SetDigestModeResult,
 } from './NotificationPreferencesUseCases';
 import type { INotificationPreferenceRepository } from '../../domain/repositories/INotificationPreferenceRepository';
 import type { NotificationPreference , ChannelPreference, TypePreference } from '../../domain/entities/NotificationPreference';
-import type { Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import type { NotificationChannel, NotificationType } from '../../domain/types/NotificationTypes';
 import { NotificationDomainError } from '../../domain/errors/NotificationDomainError';
 
@@ -19,38 +31,46 @@ describe('NotificationPreferencesUseCases', () => {
   };
   let logger: Logger;
 
-  beforeEach(() => {
-    preferenceRepository = {
-      getOrCreateDefault: vi.fn(),
-      save: vi.fn(),
-    } as unknown as INotificationPreferenceRepository as any;
-
-    logger = {
-      debug: vi.fn(),
-      info: vi.fn(),
-      warn: vi.fn(),
-      error: vi.fn(),
-    } as unknown as Logger;
-  });
-
-  it('GetNotificationPreferencesQuery returns preferences from repository', async () => {
-    const preference = {
-      id: 'pref-1',
-    } as unknown as NotificationPreference;
-
-    preferenceRepository.getOrCreateDefault.mockResolvedValue(preference);
-
-    const useCase = new GetNotificationPreferencesQuery(
-      preferenceRepository as unknown as INotificationPreferenceRepository,
-      logger,
-    );
-
-    const result = await useCase.execute('driver-1');
-
-    expect(preferenceRepository.getOrCreateDefault).toHaveBeenCalledWith('driver-1');
-    expect(result).toBe(preference);
-  });
-
+  
+    beforeEach(() => {
+      preferenceRepository = {
+        getOrCreateDefault: vi.fn(),
+        save: vi.fn(),
+      } as unknown as INotificationPreferenceRepository as any;
+  
+      logger = {
+        debug: vi.fn(),
+        info: vi.fn(),
+        warn: vi.fn(),
+        error: vi.fn(),
+      } as unknown as Logger;
+    });
+  
+    it('GetNotificationPreferencesQuery returns preferences from repository', async () => {
+      const preference = {
+        id: 'pref-1',
+      } as unknown as NotificationPreference;
+  
+      preferenceRepository.getOrCreateDefault.mockResolvedValue(preference);
+  
+      const output: UseCaseOutputPort<GetNotificationPreferencesResult> & { present: Mock } = {
+        present: vi.fn(),
+      } as any;
+  
+      const useCase = new GetNotificationPreferencesQuery(
+        preferenceRepository as unknown as INotificationPreferenceRepository,
+        output,
+        logger,
+      );
+  
+      const input: GetNotificationPreferencesInput = { driverId: 'driver-1' };
+      const result = await useCase.execute(input);
+  
+      expect(preferenceRepository.getOrCreateDefault).toHaveBeenCalledWith('driver-1');
+      expect(result).toBeInstanceOf(Result);
+      expect(result.isOk()).toBe(true);
+      expect(output.present).toHaveBeenCalledWith({ preference });
+    });
   it('UpdateChannelPreferenceUseCase updates channel preference', async () => {
     const preference = {
       updateChannel: vi.fn().mockReturnThis(),
@@ -58,19 +78,28 @@ describe('NotificationPreferencesUseCases', () => {
 
     preferenceRepository.getOrCreateDefault.mockResolvedValue(preference);
 
+    const output: UseCaseOutputPort<UpdateChannelPreferenceResult> & { present: Mock } = {
+      present: vi.fn(),
+    } as any;
+
     const useCase = new UpdateChannelPreferenceUseCase(
       preferenceRepository as unknown as INotificationPreferenceRepository,
+      output,
       logger,
     );
 
-    await useCase.execute({
+    const command: UpdateChannelPreferenceCommand = {
       driverId: 'driver-1',
       channel: 'email' as NotificationChannel,
-      preference: 'enabled' as ChannelPreference,
-    });
+      preference: { enabled: true } as ChannelPreference,
+    };
 
+    const result = await useCase.execute(command);
+
+    expect(result.isOk()).toBe(true);
     expect(preference.updateChannel).toHaveBeenCalled();
     expect(preferenceRepository.save).toHaveBeenCalledWith(preference);
+    expect(output.present).toHaveBeenCalledWith({ driverId: 'driver-1', channel: 'email' });
   });
 
   it('UpdateTypePreferenceUseCase updates type preference', async () => {
@@ -80,19 +109,28 @@ describe('NotificationPreferencesUseCases', () => {
 
     preferenceRepository.getOrCreateDefault.mockResolvedValue(preference);
 
+    const output: UseCaseOutputPort<UpdateTypePreferenceResult> & { present: Mock } = {
+      present: vi.fn(),
+    } as any;
+
     const useCase = new UpdateTypePreferenceUseCase(
       preferenceRepository as unknown as INotificationPreferenceRepository,
+      output,
       logger,
     );
 
-    await useCase.execute({
+    const command: UpdateTypePreferenceCommand = {
       driverId: 'driver-1',
-      type: 'info' as NotificationType,
-      preference: 'enabled' as TypePreference,
-    });
+      type: 'system_announcement' as NotificationType,
+      preference: { enabled: true } as TypePreference,
+    };
 
+    const result = await useCase.execute(command);
+
+    expect(result.isOk()).toBe(true);
     expect(preference.updateTypePreference).toHaveBeenCalled();
     expect(preferenceRepository.save).toHaveBeenCalledWith(preference);
+    expect(output.present).toHaveBeenCalledWith({ driverId: 'driver-1', type: 'system_announcement' });
   });
 
   it('UpdateQuietHoursUseCase validates hours and updates preferences', async () => {
@@ -102,34 +140,56 @@ describe('NotificationPreferencesUseCases', () => {
 
     preferenceRepository.getOrCreateDefault.mockResolvedValue(preference);
 
+    const output: UseCaseOutputPort<UpdateQuietHoursResult> & { present: Mock } = {
+      present: vi.fn(),
+    } as any;
+
     const useCase = new UpdateQuietHoursUseCase(
       preferenceRepository as unknown as INotificationPreferenceRepository,
+      output,
       logger,
     );
 
-    await useCase.execute({
+    const command: UpdateQuietHoursCommand = {
+      driverId: 'driver-1',
+      startHour: 22,
+      endHour: 7,
+    };
+
+    const result = await useCase.execute(command);
+
+    expect(result.isOk()).toBe(true);
+    expect(preference.updateQuietHours).toHaveBeenCalledWith(22, 7);
+    expect(preferenceRepository.save).toHaveBeenCalledWith(preference);
+    expect(output.present).toHaveBeenCalledWith({
       driverId: 'driver-1',
       startHour: 22,
       endHour: 7,
     });
-
-    expect(preference.updateQuietHours).toHaveBeenCalledWith(22, 7);
-    expect(preferenceRepository.save).toHaveBeenCalledWith(preference);
   });
 
-  it('UpdateQuietHoursUseCase throws on invalid hours', async () => {
+  it('UpdateQuietHoursUseCase returns error on invalid hours', async () => {
+    const output: UseCaseOutputPort<UpdateQuietHoursResult> & { present: Mock } = {
+      present: vi.fn(),
+    } as any;
+
     const useCase = new UpdateQuietHoursUseCase(
       preferenceRepository as unknown as INotificationPreferenceRepository,
+      output,
       logger,
     );
 
-    await expect(
-      useCase.execute({ driverId: 'd1', startHour: -1, endHour: 10 }),
-    ).rejects.toThrow(NotificationDomainError);
+    const badStart: UpdateQuietHoursCommand = { driverId: 'd1', startHour: -1, endHour: 10 };
+    const result1 = await useCase.execute(badStart);
+    expect(result1.isErr()).toBe(true);
+    const err1 = result1.unwrapErr() as ApplicationErrorCode<'INVALID_START_HOUR', { message: string }>;
+    expect(err1.code).toBe('INVALID_START_HOUR');
 
-    await expect(
-      useCase.execute({ driverId: 'd1', startHour: 10, endHour: 24 }),
-    ).rejects.toThrow(NotificationDomainError);
+    const badEnd: UpdateQuietHoursCommand = { driverId: 'd1', startHour: 10, endHour: 24 };
+    const result2 = await useCase.execute(badEnd);
+    expect(result2.isErr()).toBe(true);
+    const err2 = result2.unwrapErr() as ApplicationErrorCode<'INVALID_END_HOUR', { message: string }>;
+    expect(err2.code).toBe('INVALID_END_HOUR');
   });
 
   it('SetDigestModeUseCase sets digest mode with valid frequency', async () => {
@@ -139,27 +199,52 @@ describe('NotificationPreferencesUseCases', () => {
 
     preferenceRepository.getOrCreateDefault.mockResolvedValue(preference);
 
+    const output: UseCaseOutputPort<SetDigestModeResult> & { present: Mock } = {
+      present: vi.fn(),
+    } as any;
+
     const useCase = new SetDigestModeUseCase(
       preferenceRepository as unknown as INotificationPreferenceRepository,
+      output,
     );
 
-    await useCase.execute({
+    const command: SetDigestModeCommand = {
+      driverId: 'driver-1',
+      enabled: true,
+      frequencyHours: 4,
+    };
+
+    const result = await useCase.execute(command);
+
+    expect(result.isOk()).toBe(true);
+    expect(preference.setDigestMode).toHaveBeenCalledWith(true, 4);
+    expect(preferenceRepository.save).toHaveBeenCalledWith(preference);
+    expect(output.present).toHaveBeenCalledWith({
       driverId: 'driver-1',
       enabled: true,
       frequencyHours: 4,
     });
-
-    expect(preference.setDigestMode).toHaveBeenCalledWith(true, 4);
-    expect(preferenceRepository.save).toHaveBeenCalledWith(preference);
   });
 
-  it('SetDigestModeUseCase throws on invalid frequency', async () => {
+  it('SetDigestModeUseCase returns error on invalid frequency', async () => {
+    const output: UseCaseOutputPort<SetDigestModeResult> & { present: Mock } = {
+      present: vi.fn(),
+    } as any;
+
     const useCase = new SetDigestModeUseCase(
       preferenceRepository as unknown as INotificationPreferenceRepository,
+      output,
     );
 
-    await expect(
-      useCase.execute({ driverId: 'driver-1', enabled: true, frequencyHours: 0 }),
-    ).rejects.toThrow(NotificationDomainError);
+    const command: SetDigestModeCommand = {
+      driverId: 'driver-1',
+      enabled: true,
+      frequencyHours: 0,
+    };
+
+    const result = await useCase.execute(command);
+    expect(result.isErr()).toBe(true);
+    const err = result.unwrapErr() as ApplicationErrorCode<'INVALID_FREQUENCY', { message: string }>;
+    expect(err.code).toBe('INVALID_FREQUENCY');
   });
 });

core/notifications/application/use-cases/NotificationPreferencesUseCases.ts

@@ -4,7 +4,9 @@
  * Manages user notification preferences.
  */
 
-import type { AsyncUseCase , Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import { NotificationPreference } from '../../domain/entities/NotificationPreference';
 import type { ChannelPreference, TypePreference } from '../../domain/entities/NotificationPreference';
 import type { INotificationPreferenceRepository } from '../../domain/repositories/INotificationPreferenceRepository';
@@ -14,21 +16,40 @@ import { NotificationDomainError } from '../../domain/errors/NotificationDomainE
 /**
  * Query: GetNotificationPreferencesQuery
  */
-export class GetNotificationPreferencesQuery implements AsyncUseCase<string, NotificationPreference> {
+export interface GetNotificationPreferencesInput {
+  driverId: string;
+}
+
+export interface GetNotificationPreferencesResult {
+  preference: NotificationPreference;
+}
+
+export type GetNotificationPreferencesErrorCode = 'REPOSITORY_ERROR';
+
+export class GetNotificationPreferencesQuery {
   constructor(
     private readonly preferenceRepository: INotificationPreferenceRepository,
+    private readonly output: UseCaseOutputPort<GetNotificationPreferencesResult>,
     private readonly logger: Logger,
   ) {}
 
-  async execute(driverId: string): Promise<NotificationPreference> {
+  async execute(
+    input: GetNotificationPreferencesInput,
+  ): Promise<Result<void, ApplicationErrorCode<GetNotificationPreferencesErrorCode, { message: string }>>> {
+    const { driverId } = input;
     this.logger.debug(`Fetching notification preferences for driver: ${driverId}`);
     try {
       const preferences = await this.preferenceRepository.getOrCreateDefault(driverId);
       this.logger.info(`Successfully fetched preferences for driver: ${driverId}`);
-      return preferences;
+      this.output.present({ preference: preferences });
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error(`Failed to fetch preferences for driver: ${driverId}`, error);
-      throw error;
+      const err = error instanceof Error ? error : new Error(String(error));
+      this.logger.error(`Failed to fetch preferences for driver: ${driverId}`, err);
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
+      });
     }
   }
 }
@@ -42,22 +63,48 @@ export interface UpdateChannelPreferenceCommand {
   preference: ChannelPreference;
 }
 
-export class UpdateChannelPreferenceUseCase implements AsyncUseCase<UpdateChannelPreferenceCommand, void> {
+export interface UpdateChannelPreferenceResult {
+  driverId: string;
+  channel: NotificationChannel;
+}
+
+export type UpdateChannelPreferenceErrorCode =
+  | 'REPOSITORY_ERROR';
+
+export class UpdateChannelPreferenceUseCase {
   constructor(
     private readonly preferenceRepository: INotificationPreferenceRepository,
+    private readonly output: UseCaseOutputPort<UpdateChannelPreferenceResult>,
     private readonly logger: Logger,
   ) {}
 
-  async execute(command: UpdateChannelPreferenceCommand): Promise<void> {
-    this.logger.debug(`Updating channel preference for driver: ${command.driverId}, channel: ${command.channel}, preference: ${command.preference}`);
+  async execute(
+    command: UpdateChannelPreferenceCommand,
+  ): Promise<Result<void, ApplicationErrorCode<UpdateChannelPreferenceErrorCode, { message: string }>>> {
+    this.logger.debug(
+      `Updating channel preference for driver: ${command.driverId}, channel: ${command.channel}, preference: ${JSON.stringify(command.preference)}`,
+    );
     try {
-      const preferences = await this.preferenceRepository.getOrCreateDefault(command.driverId);
+      const preferences = await this.preferenceRepository.getOrCreateDefault(
+        command.driverId,
+      );
       const updated = preferences.updateChannel(command.channel, command.preference);
       await this.preferenceRepository.save(updated);
-      this.logger.info(`Successfully updated channel preference for driver: ${command.driverId}`);
+      this.logger.info(
+        `Successfully updated channel preference for driver: ${command.driverId}`,
+      );
+      this.output.present({ driverId: command.driverId, channel: command.channel });
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error(`Failed to update channel preference for driver: ${command.driverId}, channel: ${command.channel}`, error);
-      throw error;
+      const err = error instanceof Error ? error : new Error(String(error));
+      this.logger.error(
+        `Failed to update channel preference for driver: ${command.driverId}, channel: ${command.channel}`,
+        err,
+      );
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
+      });
     }
   }
 }
@@ -71,22 +118,47 @@ export interface UpdateTypePreferenceCommand {
   preference: TypePreference;
 }
 
-export class UpdateTypePreferenceUseCase implements AsyncUseCase<UpdateTypePreferenceCommand, void> {
+export interface UpdateTypePreferenceResult {
+  driverId: string;
+  type: NotificationType;
+}
+
+export type UpdateTypePreferenceErrorCode = 'REPOSITORY_ERROR';
+
+export class UpdateTypePreferenceUseCase {
   constructor(
     private readonly preferenceRepository: INotificationPreferenceRepository,
+    private readonly output: UseCaseOutputPort<UpdateTypePreferenceResult>,
     private readonly logger: Logger,
   ) {}
 
-  async execute(command: UpdateTypePreferenceCommand): Promise<void> {
-    this.logger.debug(`Updating type preference for driver: ${command.driverId}, type: ${command.type}, preference: ${command.preference}`);
+  async execute(
+    command: UpdateTypePreferenceCommand,
+  ): Promise<Result<void, ApplicationErrorCode<UpdateTypePreferenceErrorCode, { message: string }>>> {
+    this.logger.debug(
+      `Updating type preference for driver: ${command.driverId}, type: ${command.type}, preference: ${JSON.stringify(command.preference)}`,
+    );
     try {
-      const preferences = await this.preferenceRepository.getOrCreateDefault(command.driverId);
+      const preferences = await this.preferenceRepository.getOrCreateDefault(
+        command.driverId,
+      );
       const updated = preferences.updateTypePreference(command.type, command.preference);
       await this.preferenceRepository.save(updated);
-      this.logger.info(`Successfully updated type preference for driver: ${command.driverId}`);
+      this.logger.info(
+        `Successfully updated type preference for driver: ${command.driverId}`,
+      );
+      this.output.present({ driverId: command.driverId, type: command.type });
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error(`Failed to update type preference for driver: ${command.driverId}, type: ${command.type}`, error);
-      throw error;
+      const err = error instanceof Error ? error : new Error(String(error));
+      this.logger.error(
+        `Failed to update type preference for driver: ${command.driverId}, type: ${command.type}`,
+        err,
+      );
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
+      });
     }
   }
 }
@@ -100,32 +172,73 @@ export interface UpdateQuietHoursCommand {
   endHour: number | undefined;
 }
 
-export class UpdateQuietHoursUseCase implements AsyncUseCase<UpdateQuietHoursCommand, void> {
+export interface UpdateQuietHoursResult {
+  driverId: string;
+  startHour: number | undefined;
+  endHour: number | undefined;
+}
+
+export type UpdateQuietHoursErrorCode =
+  | 'INVALID_START_HOUR'
+  | 'INVALID_END_HOUR'
+  | 'REPOSITORY_ERROR';
+
+export class UpdateQuietHoursUseCase {
   constructor(
     private readonly preferenceRepository: INotificationPreferenceRepository,
+    private readonly output: UseCaseOutputPort<UpdateQuietHoursResult>,
     private readonly logger: Logger,
   ) {}
 
-  async execute(command: UpdateQuietHoursCommand): Promise<void> {
-    this.logger.debug(`Updating quiet hours for driver: ${command.driverId}, startHour: ${command.startHour}, endHour: ${command.endHour}`);
+  async execute(
+    command: UpdateQuietHoursCommand,
+  ): Promise<Result<void, ApplicationErrorCode<UpdateQuietHoursErrorCode, { message: string }>>> {
+    this.logger.debug(
+      `Updating quiet hours for driver: ${command.driverId}, startHour: ${command.startHour}, endHour: ${command.endHour}`,
+    );
     try {
       // Validate hours if provided
       if (command.startHour !== undefined && (command.startHour < 0 || command.startHour > 23)) {
-        this.logger.warn(`Invalid start hour provided for driver: ${command.driverId}. startHour: ${command.startHour}`);
-        throw new NotificationDomainError('Start hour must be between 0 and 23');
+        this.logger.warn(
+          `Invalid start hour provided for driver: ${command.driverId}. startHour: ${command.startHour}`,
+        );
+        return Result.err({
+          code: 'INVALID_START_HOUR',
+          details: { message: 'Start hour must be between 0 and 23' },
+        });
       }
       if (command.endHour !== undefined && (command.endHour < 0 || command.endHour > 23)) {
-        this.logger.warn(`Invalid end hour provided for driver: ${command.driverId}. endHour: ${command.endHour}`);
-        throw new NotificationDomainError('End hour must be between 0 and 23');
+        this.logger.warn(
+          `Invalid end hour provided for driver: ${command.driverId}. endHour: ${command.endHour}`,
+        );
+        return Result.err({
+          code: 'INVALID_END_HOUR',
+          details: { message: 'End hour must be between 0 and 23' },
+        });
       }
 
-      const preferences = await this.preferenceRepository.getOrCreateDefault(command.driverId);
-      const updated = preferences.updateQuietHours(command.startHour, command.endHour);
+      const preferences = await this.preferenceRepository.getOrCreateDefault(
+        command.driverId,
+      );
+      const updated = preferences.updateQuietHours(
+        command.startHour,
+        command.endHour,
+      );
       await this.preferenceRepository.save(updated);
       this.logger.info(`Successfully updated quiet hours for driver: ${command.driverId}`);
+      this.output.present({
+        driverId: command.driverId,
+        startHour: command.startHour,
+        endHour: command.endHour,
+      });
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error(`Failed to update quiet hours for driver: ${command.driverId}`, error);
-      throw error;
+      const err = error instanceof Error ? error : new Error(String(error));
+      this.logger.error(`Failed to update quiet hours for driver: ${command.driverId}`, err);
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
+      });
     }
   }
 }
@@ -139,18 +252,53 @@ export interface SetDigestModeCommand {
   frequencyHours?: number;
 }
 
-export class SetDigestModeUseCase implements AsyncUseCase<SetDigestModeCommand, void> {
+export interface SetDigestModeResult {
+  driverId: string;
+  enabled: boolean;
+  frequencyHours?: number;
+}
+
+export type SetDigestModeErrorCode =
+  | 'INVALID_FREQUENCY'
+  | 'REPOSITORY_ERROR';
+
+export class SetDigestModeUseCase {
   constructor(
     private readonly preferenceRepository: INotificationPreferenceRepository,
+    private readonly output: UseCaseOutputPort<SetDigestModeResult>,
   ) {}
 
-  async execute(command: SetDigestModeCommand): Promise<void> {
+  async execute(
+    command: SetDigestModeCommand,
+  ): Promise<Result<void, ApplicationErrorCode<SetDigestModeErrorCode, { message: string }>>> {
     if (command.frequencyHours !== undefined && command.frequencyHours < 1) {
-      throw new NotificationDomainError('Digest frequency must be at least 1 hour');
+      return Result.err({
+        code: 'INVALID_FREQUENCY',
+        details: { message: 'Digest frequency must be at least 1 hour' },
+      });
     }
 
-    const preferences = await this.preferenceRepository.getOrCreateDefault(command.driverId);
-    const updated = preferences.setDigestMode(command.enabled, command.frequencyHours);
-    await this.preferenceRepository.save(updated);
+    try {
+      const preferences = await this.preferenceRepository.getOrCreateDefault(
+        command.driverId,
+      );
+      const updated = preferences.setDigestMode(
+        command.enabled,
+        command.frequencyHours,
+      );
+      await this.preferenceRepository.save(updated);
+      this.output.present({
+        driverId: command.driverId,
+        enabled: command.enabled,
+        frequencyHours: command.frequencyHours,
+      });
+      return Result.ok(undefined);
+    } catch (error) {
+      const err = error instanceof Error ? error : new Error(String(error));
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
+      });
+    }
   }
 }

core/notifications/application/use-cases/SendNotificationUseCase.ts

@@ -5,7 +5,9 @@
  * based on their preferences.
  */
 
-import type { AsyncUseCase, Logger } from '@core/shared/application';
+import type { Logger, UseCaseOutputPort } from '@core/shared/application';
+import { Result } from '@core/shared/application/Result';
+import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import { v4 as uuid } from 'uuid';
 import type { NotificationData } from '../../domain/entities/Notification';
 import { Notification } from '../../domain/entities/Notification';
@@ -43,17 +45,22 @@ export interface SendNotificationResult {
   deliveryResults: NotificationDeliveryResult[];
 }
 
-export class SendNotificationUseCase implements AsyncUseCase<SendNotificationCommand, SendNotificationResult> {
+export type SendNotificationErrorCode = 'REPOSITORY_ERROR';
+
+export class SendNotificationUseCase {
   constructor(
     private readonly notificationRepository: INotificationRepository,
     private readonly preferenceRepository: INotificationPreferenceRepository,
     private readonly gatewayRegistry: NotificationGatewayRegistry,
+    private readonly output: UseCaseOutputPort<SendNotificationResult>,
     private readonly logger: Logger,
   ) {
     this.logger.debug('SendNotificationUseCase initialized.');
   }
 
-  async execute(command: SendNotificationCommand): Promise<SendNotificationResult> {
+  async execute(
+    command: SendNotificationCommand,
+  ): Promise<Result<void, ApplicationErrorCode<SendNotificationErrorCode, { message: string }>>> {
     this.logger.debug('Executing SendNotificationUseCase', { command });
     try {
       // Get recipient's preferences
@@ -84,7 +91,8 @@ export class SendNotificationUseCase implements AsyncUseCase<SendNotificationCom
       }
   
       // Determine which channels to use
-      const channels = command.forceChannels ?? preferences.getEnabledChannelsForType(command.type);
+      const channels =
+        command.forceChannels ?? preferences.getEnabledChannelsForType(command.type);
   
       // Check quiet hours (skip external channels during quiet hours)
       const effectiveChannels = preferences.isInQuietHours()
@@ -133,13 +141,19 @@ export class SendNotificationUseCase implements AsyncUseCase<SendNotificationCom
         }
       }
   
-      return {
+      this.output.present({
         notification: primaryNotification!,
         deliveryResults,
-      };
+      });
+
+      return Result.ok(undefined);
     } catch (error) {
-      this.logger.error('Error sending notification', error as Error);
-      throw error;
+      const err = error instanceof Error ? error : new Error(String(error));
+      this.logger.error('Error sending notification', err);
+      return Result.err({
+        code: 'REPOSITORY_ERROR',
+        details: { message: err.message },
+      });
     }
   }
 }

core/racing/application/services/SeasonApplicationService.ts

@@ -1,18 +1,20 @@
+import { v4 as uuidv4 } from 'uuid';
 import { Season } from '../../domain/entities/Season';
-import type { ISeasonRepository } from '../../domain/repositories/ISeasonRepository';
 import type { ILeagueRepository } from '../../domain/repositories/ILeagueRepository';
-import type { LeagueConfigFormModel } from '../dto/LeagueConfigFormDTO';
+import type { ISeasonRepository } from '../../domain/repositories/ISeasonRepository';
+import type { Weekday } from '../../domain/types/Weekday';
+import { LeagueTimezone } from '../../domain/value-objects/LeagueTimezone';
+import { MonthlyRecurrencePattern } from '../../domain/value-objects/MonthlyRecurrencePattern';
+import { RaceTimeOfDay } from '../../domain/value-objects/RaceTimeOfDay';
+import { RecurrenceStrategyFactory } from '../../domain/value-objects/RecurrenceStrategy';
+import { SeasonDropPolicy } from '../../domain/value-objects/SeasonDropPolicy';
 import { SeasonSchedule } from '../../domain/value-objects/SeasonSchedule';
 import { SeasonScoringConfig } from '../../domain/value-objects/SeasonScoringConfig';
-import { SeasonDropPolicy } from '../../domain/value-objects/SeasonDropPolicy';
 import { SeasonStewardingConfig } from '../../domain/value-objects/SeasonStewardingConfig';
-import { RaceTimeOfDay } from '../../domain/value-objects/RaceTimeOfDay';
-import { LeagueTimezone } from '../../domain/value-objects/LeagueTimezone';
-import { RecurrenceStrategyFactory } from '../../domain/value-objects/RecurrenceStrategy';
 import { WeekdaySet } from '../../domain/value-objects/WeekdaySet';
-import { MonthlyRecurrencePattern } from '../../domain/value-objects/MonthlyRecurrencePattern';
-import type { Weekday } from '../../domain/types/Weekday';
-import { v4 as uuidv4 } from 'uuid';
+import type { LeagueConfigFormModel } from '../dto/LeagueConfigFormDTO';
+
+// TODO The whole file mixes a lot of concerns...
 
 export interface CreateSeasonForLeagueCommand {
   leagueId: string;

core/racing/application/use-cases/CompleteDriverOnboardingUseCase.test.ts

@@ -1,9 +1,15 @@
 import { describe, it, expect, beforeEach, vi, Mock } from 'vitest';
-import { CompleteDriverOnboardingUseCase, type CompleteDriverOnboardingResult } from './CompleteDriverOnboardingUseCase';
+import {
+  CompleteDriverOnboardingUseCase,
+  type CompleteDriverOnboardingInput,
+  type CompleteDriverOnboardingResult,
+  type CompleteDriverOnboardingApplicationError,
+} from './CompleteDriverOnboardingUseCase';
 import type { IDriverRepository } from '../../domain/repositories/IDriverRepository';
 import { Driver } from '../../domain/entities/Driver';
-import type { CompleteDriverOnboardingInput } from './CompleteDriverOnboardingUseCase';
 import type { UseCaseOutputPort } from '@core/shared/application/UseCaseOutputPort';
+import type { Logger } from '@core/shared/application/Logger';
+import type { Result } from '@core/shared/application/Result';
 
 describe('CompleteDriverOnboardingUseCase', () => {
   let useCase: CompleteDriverOnboardingUseCase;
@@ -11,17 +17,25 @@ describe('CompleteDriverOnboardingUseCase', () => {
     findById: Mock;
     create: Mock;
   };
-  let output: { present: Mock };
+  let logger: Logger & { error: Mock };
+  let output: { present: Mock } & UseCaseOutputPort<CompleteDriverOnboardingResult>;
 
   beforeEach(() => {
     driverRepository = {
       findById: vi.fn(),
       create: vi.fn(),
     };
-    output = { present: vi.fn() };
+    logger = {
+      debug: vi.fn(),
+      info: vi.fn(),
+      warn: vi.fn(),
+      error: vi.fn(),
+    } as unknown as Logger & { error: Mock };
+    output = { present: vi.fn() } as unknown as typeof output;
     useCase = new CompleteDriverOnboardingUseCase(
       driverRepository as unknown as IDriverRepository,
-      output as unknown as UseCaseOutputPort<CompleteDriverOnboardingResult>,
+      logger,
+      output,
     );
   });
 

core/racing/application/use-cases/CompleteDriverOnboardingUseCase.ts

@@ -3,6 +3,7 @@ import { Driver } from '../../domain/entities/Driver';
 import { Result } from '@core/shared/application/Result';
 import type { ApplicationErrorCode } from '@core/shared/errors/ApplicationErrorCode';
 import type { UseCaseOutputPort } from '@core/shared/application/UseCaseOutputPort';
+import type { Logger } from '@core/shared/application/Logger';
 
 export interface CompleteDriverOnboardingInput {
   userId: string;
@@ -17,28 +18,43 @@ export type CompleteDriverOnboardingResult = {
   driver: Driver;
 };
 
+export type CompleteDriverOnboardingErrorCode =
+  | 'DRIVER_ALREADY_EXISTS'
+  | 'REPOSITORY_ERROR';
+
+export type CompleteDriverOnboardingApplicationError = ApplicationErrorCode<
+  CompleteDriverOnboardingErrorCode,
+  { message: string }
+>;
+
 /**
  * Use Case for completing driver onboarding.
  */
 export class CompleteDriverOnboardingUseCase {
   constructor(
     private readonly driverRepository: IDriverRepository,
+    private readonly logger: Logger,
     private readonly output: UseCaseOutputPort<CompleteDriverOnboardingResult>,
   ) {}
 
-  async execute(command: CompleteDriverOnboardingInput): Promise<Result<void, ApplicationErrorCode<'DRIVER_ALREADY_EXISTS' | 'REPOSITORY_ERROR'>>> {
+  async execute(
+    input: CompleteDriverOnboardingInput,
+  ): Promise<Result<void, CompleteDriverOnboardingApplicationError>> {
     try {
-      const existing = await this.driverRepository.findById(command.userId);
+      const existing = await this.driverRepository.findById(input.userId);
       if (existing) {
-        return Result.err({ code: 'DRIVER_ALREADY_EXISTS' });
+        return Result.err({
+          code: 'DRIVER_ALREADY_EXISTS',
+          details: { message: 'Driver already exists' },
+        });
       }
 
       const driver = Driver.create({
-        id: command.userId,
-        iracingId: command.userId,
-        name: command.displayName,
-        country: command.country,
-        ...(command.bio !== undefined ? { bio: command.bio } : {}),
+        id: input.userId,
+        iracingId: input.userId,
+        name: input.displayName,
+        country: input.country,
+        ...(input.bio !== undefined ? { bio: input.bio } : {}),
       });
 
       await this.driverRepository.create(driver);
@@ -47,10 +63,16 @@ export class CompleteDriverOnboardingUseCase {
 
       return Result.ok(undefined);
     } catch (error) {
+      const err = error instanceof Error ? error : new Error('Unknown error');
+
+      this.logger.error('CompleteDriverOnboardingUseCase.execute failed', err, {
+        input,
+      });
+
       return Result.err({
         code: 'REPOSITORY_ERROR',
         details: {
-          message: error instanceof Error ? error.message : 'Unknown error',
+          message: err.message ?? 'Unexpected repository error',
         },
       });
     }

docs/architecture/DOMAIN_OBJECTS.md

@@ -0,0 +1,264 @@
+Domain Objects Design Guide (Clean Architecture)
+
+This document defines all domain object types used in the Core and assigns strict responsibilities and boundaries.
+
+Its goal is to remove ambiguity between:
+	•	Entities
+	•	Value Objects
+	•	Aggregate Roots
+	•	Domain Services
+	•	Domain Events
+
+The rules in this document are non-negotiable.
+
+⸻
+
+Core Principle
+
+Domain objects represent business truth.
+
+They:
+	•	outlive APIs and UIs
+	•	must remain stable over time
+	•	must not depend on technical details
+
+If a class answers a business question, it belongs here.
+
+⸻
+
+1. Entities
+
+Definition
+
+An Entity is a domain object that:
+	•	has a stable identity
+	•	changes over time
+	•	represents a business concept
+
+Identity matters more than attributes.
+
+⸻
+
+Responsibilities
+
+Entities MUST:
+	•	own their identity
+	•	enforce invariants on state changes
+	•	expose behavior, not setters
+
+Entities MUST NOT:
+	•	depend on DTOs or transport models
+	•	access repositories or services
+	•	perform IO
+	•	know about frameworks
+
+⸻
+
+Creation Rules
+	•	New entities are created via create()
+	•	Existing entities are reconstructed via rehydrate()
+
+core/<context>/domain/entities/
+
+
+⸻
+
+Example
+	•	League
+	•	Season
+	•	Race
+	•	Driver
+
+⸻
+
+2. Value Objects
+
+Definition
+
+A Value Object is a domain object that:
+	•	has no identity
+	•	is immutable
+	•	is defined by its value
+
+⸻
+
+Responsibilities
+
+Value Objects MUST:
+	•	validate their own invariants
+	•	be immutable
+	•	be comparable by value
+
+Value Objects MUST NOT:
+	•	contain business workflows
+	•	reference entities
+	•	perform IO
+
+⸻
+
+Creation Rules
+	•	create() for new domain meaning
+	•	fromX() for interpreting external formats
+
+core/<context>/domain/value-objects/
+
+
+⸻
+
+Example
+	•	Money
+	•	LeagueName
+	•	RaceTimeOfDay
+	•	SeasonSchedule
+
+⸻
+
+3. Aggregate Roots
+
+Definition
+
+An Aggregate Root is an entity that:
+	•	acts as the consistency boundary
+	•	protects invariants across related entities
+
+All access to the aggregate happens through the root.
+
+⸻
+
+Responsibilities
+
+Aggregate Roots MUST:
+	•	enforce consistency rules
+	•	control modifications of child entities
+
+Aggregate Roots MUST NOT:
+	•	expose internal collections directly
+	•	allow partial updates bypassing rules
+
+⸻
+
+Example
+	•	League (root)
+	•	Season (root)
+
+⸻
+
+4. Domain Services
+
+Definition
+
+A Domain Service encapsulates domain logic that:
+	•	does not naturally belong to a single entity
+	•	involves multiple domain objects
+
+⸻
+
+Responsibilities
+
+Domain Services MAY:
+	•	coordinate entities
+	•	calculate derived domain values
+
+Domain Services MUST:
+	•	operate only on domain types
+	•	remain stateless
+
+Domain Services MUST NOT:
+	•	access repositories
+	•	orchestrate use cases
+	•	perform IO
+
+core/<context>/domain/services/
+
+
+⸻
+
+Example
+	•	SeasonConfigurationFactory
+	•	ChampionshipAggregator
+	•	StrengthOfFieldCalculator
+
+⸻
+
+5. Domain Events
+
+Definition
+
+A Domain Event represents something that:
+	•	has already happened
+	•	is important to the business
+
+⸻
+
+Responsibilities
+
+Domain Events MUST:
+	•	be immutable
+	•	carry minimal information
+
+Domain Events MUST NOT:
+	•	contain behavior
+	•	perform side effects
+
+core/<context>/domain/events/
+
+
+⸻
+
+Example
+	•	RaceCompleted
+	•	SeasonActivated
+
+⸻
+
+6. What Does NOT Belong in Domain Objects
+
+❌ DTOs
+❌ API Models
+❌ View Models
+❌ Repositories
+❌ Framework Types
+❌ Logging
+❌ Configuration
+
+If it depends on infrastructure, it does not belong here.
+
+⸻
+
+7. Dependency Rules
+
+Entities → Value Objects
+Entities → Domain Services
+Domain Services → Entities
+
+Reverse dependencies are forbidden.
+
+⸻
+
+8. Testing Requirements
+
+Domain Objects MUST:
+	•	have unit tests for invariants
+	•	be tested without mocks
+
+Domain Services MUST:
+	•	have deterministic tests
+
+⸻
+
+Mental Model (Final)
+
+Entities protect state.
+Value Objects protect meaning.
+Aggregate Roots protect consistency.
+Domain Services protect cross-entity rules.
+Domain Events describe facts.
+
+⸻
+
+Final Summary
+	•	Domain objects represent business truth
+	•	They are pure and framework-free
+	•	They form the most stable part of the system
+
+If domain objects are clean, everything else becomes easier.

docs/architecture/SERVICES.md

@@ -0,0 +1,252 @@
+Services Design Guide (Clean Architecture)
+
+This document defines all service types used across the system and assigns clear, non-overlapping responsibilities.
+
+It exists to remove ambiguity around the word “service”, which is heavily overloaded.
+
+The rules below are strict.
+
+⸻
+
+Overview
+
+The system contains four distinct service categories, each in a different layer:
+	1.	Frontend Services
+	2.	API Services
+	3.	Core Application Services
+	4.	Core Domain Services
+
+They must never be mixed.
+
+⸻
+
+1. Frontend Services
+
+Purpose
+
+Frontend services orchestrate UI-driven workflows.
+
+They answer the question:
+
+“How does the UI obtain and submit data?”
+
+⸻
+
+Responsibilities
+
+Frontend services MAY:
+	•	call API clients
+	•	apply client-side guards (blockers, throttles)
+	•	create View Models
+	•	orchestrate multiple API calls
+	•	handle recoverable UI errors
+
+Frontend services MUST NOT:
+	•	contain business rules
+	•	validate domain invariants
+	•	modify domain state
+	•	know about core domain objects
+
+⸻
+
+Placement
+
+apps/website/lib/services/
+
+
+⸻
+
+Example
+	•	LeagueService
+	•	RaceService
+	•	AuthService
+
+Each service is UI-facing, not business-facing.
+
+⸻
+
+2. API Services (Application Services)
+
+Purpose
+
+API services adapt HTTP-level concerns to core use cases.
+
+They answer the question:
+
+“How does an external client interact with the core?”
+
+⸻
+
+Responsibilities
+
+API services MAY:
+	•	orchestrate multiple use cases
+	•	perform authorization checks
+	•	map transport input to use-case input
+	•	coordinate transactions
+
+API services MUST NOT:
+	•	contain domain logic
+	•	enforce business invariants
+	•	build domain entities
+	•	return domain objects
+
+⸻
+
+Placement
+
+apps/api/**/ApplicationService.ts
+
+
+⸻
+
+Example
+	•	LeagueApplicationService
+	•	SeasonApplicationService
+
+API services are delivery-layer coordinators.
+
+⸻
+
+3. Core Application Services (Use Cases)
+
+Purpose
+
+Core application services implement business use cases.
+
+They answer the question:
+
+“What does the system do?”
+
+⸻
+
+Responsibilities
+
+Use Cases MUST:
+	•	accept primitive input only
+	•	create Value Objects
+	•	create or modify Entities
+	•	enforce business rules
+	•	call repositories via ports
+	•	communicate results via output ports
+
+Use Cases MUST NOT:
+	•	know about HTTP, UI, or frameworks
+	•	return DTOs
+	•	perform persistence directly
+
+⸻
+
+Placement
+
+core/<context>/application/commands/
+core/<context>/application/queries/
+
+
+⸻
+
+Example
+	•	CreateLeagueUseCase
+	•	ApplyPenaltyUseCase
+	•	GetLeagueStandingsQuery
+
+Use Cases define system behavior.
+
+⸻
+
+4. Core Domain Services
+
+Purpose
+
+Domain services encapsulate domain logic that does not belong to a single entity.
+
+They answer the question:
+
+“What rules exist that span multiple domain objects?”
+
+⸻
+
+Responsibilities
+
+Domain services MAY:
+	•	coordinate multiple entities
+	•	compute derived domain values
+	•	enforce cross-aggregate rules
+
+Domain services MUST:
+	•	use only domain concepts
+	•	return domain objects or primitives
+
+Domain services MUST NOT:
+	•	access repositories
+	•	depend on application services
+	•	perform IO
+
+⸻
+
+Placement
+
+core/<context>/domain/services/
+
+
+⸻
+
+Example
+	•	SeasonConfigurationFactory
+	•	ChampionshipAggregator
+	•	StrengthOfFieldCalculator
+
+Domain services protect business integrity.
+
+⸻
+
+Dependency Rules (Non-Negotiable)
+
+Frontend Service
+  → API Client
+    → API Service
+      → Core Use Case
+        → Domain Service / Entity
+
+Reverse dependencies are forbidden.
+
+⸻
+
+Anti-Patterns (Forbidden)
+
+❌ Frontend calling core directly
+❌ API service constructing domain entities
+❌ Use case returning DTOs
+❌ Domain service accessing repositories
+❌ Single class acting as multiple service types
+
+⸻
+
+Naming Conventions
+
+Layer	Naming
+Frontend	*Service
+API	*ApplicationService
+Core Application	*UseCase, *Query
+Core Domain	*Service, *Factory, *Calculator
+
+
+⸻
+
+Mental Model (Final)
+
+Services coordinate.
+Use Cases decide.
+Domain enforces truth.
+Adapters translate.
+
+If a class violates this mental model, it is in the wrong layer.
+
+⸻
+
+Final Summary
+	•	“Service” means different things in different layers
+	•	Mixing service types causes architectural decay
+	•	Clean Architecture remains simple when roles stay pure
+
+This document defines the only allowed service roles in the system.