diff --git a/packages/auth-client/src/__tests__/smartauth.test.ts b/packages/auth-client/src/__tests__/smartauth.test.ts
new file mode 100644
index 00000000..68117c4d
--- /dev/null
+++ b/packages/auth-client/src/__tests__/smartauth.test.ts
@@ -0,0 +1,518 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { createAuthClient } from '../client.js';
+import type { TokenStorage } from '../types.js';
+
+function createMockStorage(): TokenStorage & { store: Map<string, string> } {
+  const store = new Map<string, string>();
+  return {
+    store,
+    getItem: (key: string) => store.get(key) ?? null,
+    setItem: (key: string, value: string) => store.set(key, value),
+    removeItem: (key: string) => store.delete(key),
+  };
+}
+
+function mockFetchResponse(data: unknown, status = 200) {
+  return vi.fn().mockResolvedValue({
+    ok: status >= 200 && status < 300,
+    status,
+    json: () => Promise.resolve(data),
+  });
+}
+
+describe('@bytelyst/auth-client — SmartAuth', () => {
+  let storage: ReturnType<typeof createMockStorage>;
+
+  beforeEach(() => {
+    storage = createMockStorage();
+    vi.restoreAllMocks();
+  });
+
+  // ── Phase 1C: Google Sign-In ──────────────────────
+
+  describe('loginWithGoogle', () => {
+    it('calls POST /auth/oauth/google and stores tokens', async () => {
+      const mockData = {
+        accessToken: 'google-at',
+        refreshToken: 'google-rt',
+        user: { id: 'u1', email: 'g@gmail.com', displayName: 'G', role: 'user', plan: 'free' },
+      };
+      globalThis.fetch = mockFetchResponse(mockData);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+
+      const result = await client.loginWithGoogle('google-id-token-123');
+
+      expect('user' in result).toBe(true);
+      if ('user' in result) {
+        expect(result.user.email).toBe('g@gmail.com');
+      }
+      expect(client.getAccessToken()).toBe('google-at');
+      expect(client.getRefreshToken()).toBe('google-rt');
+
+      const [url, opts] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+      expect(url).toBe('http://localhost:4003/api/auth/oauth/google');
+      expect(opts.method).toBe('POST');
+      const body = JSON.parse(opts.body);
+      expect(body.idToken).toBe('google-id-token-123');
+    });
+
+    it('returns MFA challenge when mfaRequired is true', async () => {
+      const mfaData = {
+        mfaRequired: true,
+        mfaChallenge: 'challenge-token-abc',
+        methods: ['totp'],
+      };
+      globalThis.fetch = mockFetchResponse(mfaData);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+
+      const result = await client.loginWithGoogle('google-id-token-456');
+
+      expect('mfaRequired' in result).toBe(true);
+      if ('mfaRequired' in result) {
+        expect(result.mfaRequired).toBe(true);
+        expect(result.mfaChallenge).toBe('challenge-token-abc');
+        expect(result.methods).toEqual(['totp']);
+      }
+      // Tokens should NOT be stored when MFA is required
+      expect(client.isAuthenticated()).toBe(false);
+    });
+  });
+
+  describe('loginWithMicrosoft', () => {
+    it('calls POST /auth/oauth/microsoft', async () => {
+      const mockData = {
+        accessToken: 'ms-at',
+        refreshToken: 'ms-rt',
+        user: { id: 'u2', email: 'ms@outlook.com', displayName: 'MS', role: 'user', plan: 'free' },
+      };
+      globalThis.fetch = mockFetchResponse(mockData);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+
+      await client.loginWithMicrosoft('ms-id-token');
+
+      const [url] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+      expect(url).toBe('http://localhost:4003/api/auth/oauth/microsoft');
+      expect(client.getAccessToken()).toBe('ms-at');
+    });
+  });
+
+  describe('loginWithApple', () => {
+    it('calls POST /auth/oauth/apple', async () => {
+      const mockData = {
+        accessToken: 'apple-at',
+        refreshToken: 'apple-rt',
+        user: { id: 'u3', email: 'a@icloud.com', displayName: 'A', role: 'user', plan: 'free' },
+      };
+      globalThis.fetch = mockFetchResponse(mockData);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+
+      await client.loginWithApple('apple-id-token');
+
+      const [url] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+      expect(url).toBe('http://localhost:4003/api/auth/oauth/apple');
+      expect(client.getAccessToken()).toBe('apple-at');
+    });
+  });
+
+  // ── Phase 1C: Provider management ─────────────────
+
+  describe('getProviders', () => {
+    it('calls GET /auth/providers', async () => {
+      const providers = [
+        {
+          provider: 'google',
+          email: 'g@gmail.com',
+          linkedAt: '2025-01-01T00:00:00Z',
+          lastUsedAt: null,
+        },
+      ];
+      globalThis.fetch = mockFetchResponse(providers);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('tok', 'ref');
+
+      const result = await client.getProviders();
+
+      expect(result).toHaveLength(1);
+      expect(result[0].provider).toBe('google');
+
+      const [url, opts] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+      expect(url).toBe('http://localhost:4003/api/auth/providers');
+      expect(opts.method).toBe('GET');
+      expect(opts.headers['Authorization']).toBe('Bearer tok');
+    });
+  });
+
+  describe('linkProvider', () => {
+    it('calls POST /auth/providers/link with provider and idToken', async () => {
+      globalThis.fetch = mockFetchResponse({});
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('tok', 'ref');
+
+      await client.linkProvider('google', 'link-token');
+
+      const [url, opts] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+      expect(url).toBe('http://localhost:4003/api/auth/providers/link');
+      expect(opts.method).toBe('POST');
+      const body = JSON.parse(opts.body);
+      expect(body.provider).toBe('google');
+      expect(body.idToken).toBe('link-token');
+    });
+  });
+
+  describe('unlinkProvider', () => {
+    it('calls DELETE /auth/providers/:provider', async () => {
+      globalThis.fetch = mockFetchResponse({});
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('tok', 'ref');
+
+      await client.unlinkProvider('google');
+
+      const [url, opts] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+      expect(url).toBe('http://localhost:4003/api/auth/providers/google');
+      expect(opts.method).toBe('DELETE');
+    });
+  });
+
+  // ── Phase 2D: MFA ─────────────────────────────────
+
+  describe('verifyMfa', () => {
+    it('sends challenge token and TOTP code, stores tokens', async () => {
+      const mockData = {
+        accessToken: 'mfa-at',
+        refreshToken: 'mfa-rt',
+        user: { id: 'u1', email: 'a@b.com', displayName: 'A', role: 'user', plan: 'free' },
+      };
+      globalThis.fetch = mockFetchResponse(mockData);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+
+      const result = await client.verifyMfa('challenge-xyz', '123456', 'totp');
+
+      expect(result.user.email).toBe('a@b.com');
+      expect(client.getAccessToken()).toBe('mfa-at');
+
+      const body = JSON.parse((globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0][1].body);
+      expect(body.challengeToken).toBe('challenge-xyz');
+      expect(body.code).toBe('123456');
+      expect(body.method).toBe('totp');
+    });
+  });
+
+  describe('setupTotp', () => {
+    it('calls POST /auth/mfa/totp/setup', async () => {
+      const setup = {
+        otpauthUri: 'otpauth://totp/Test?secret=ABC',
+        qrDataUrl: 'data:image/png;base64,...',
+        recoveryCodes: ['code1', 'code2'],
+      };
+      globalThis.fetch = mockFetchResponse(setup);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('tok', 'ref');
+
+      const result = await client.setupTotp();
+
+      expect(result.otpauthUri).toContain('otpauth://');
+      expect(result.recoveryCodes).toHaveLength(2);
+
+      const [url] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+      expect(url).toBe('http://localhost:4003/api/auth/mfa/totp/setup');
+    });
+  });
+
+  describe('getMfaStatus', () => {
+    it('returns MFA status', async () => {
+      const status = { mfaEnabled: true, methods: ['totp'], recoveryCodesRemaining: 6 };
+      globalThis.fetch = mockFetchResponse(status);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('tok', 'ref');
+
+      const result = await client.getMfaStatus();
+      expect(result.mfaEnabled).toBe(true);
+      expect(result.methods).toContain('totp');
+    });
+  });
+
+  // ── Phase 3: Passkeys ─────────────────────────────
+
+  describe('listPasskeys', () => {
+    it('calls GET /auth/passkeys', async () => {
+      const passkeys = [
+        {
+          id: 'pk1',
+          friendlyName: 'MacBook',
+          deviceType: 'platform',
+          backedUp: true,
+          lastUsedAt: null,
+          createdAt: '2025-01-01T00:00:00Z',
+        },
+      ];
+      globalThis.fetch = mockFetchResponse(passkeys);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('tok', 'ref');
+
+      const result = await client.listPasskeys();
+      expect(result).toHaveLength(1);
+      expect(result[0].friendlyName).toBe('MacBook');
+    });
+  });
+
+  describe('verifyPasskeyAuth', () => {
+    it('stores tokens after passkey authentication', async () => {
+      const mockData = {
+        accessToken: 'pk-at',
+        refreshToken: 'pk-rt',
+        user: { id: 'u1', email: 'a@b.com', displayName: 'A', role: 'user', plan: 'free' },
+      };
+      globalThis.fetch = mockFetchResponse(mockData);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+
+      const result = await client.verifyPasskeyAuth({ id: 'cred-1', response: {} });
+
+      expect(result.user.email).toBe('a@b.com');
+      expect(client.getAccessToken()).toBe('pk-at');
+
+      const [url] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+      expect(url).toBe('http://localhost:4003/api/auth/passkeys/authenticate/verify');
+    });
+  });
+
+  // ── Phase 3: Devices ──────────────────────────────
+
+  describe('listDevices', () => {
+    it('calls GET /auth/devices', async () => {
+      const devices = [
+        {
+          id: 'd1',
+          name: 'Chrome on Mac',
+          platform: 'web',
+          trustLevel: 'trusted',
+          trustExpiresAt: '2025-04-01T00:00:00Z',
+          lastLoginAt: '2025-01-01T00:00:00Z',
+          createdAt: '2025-01-01T00:00:00Z',
+        },
+      ];
+      globalThis.fetch = mockFetchResponse(devices);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('tok', 'ref');
+
+      const result = await client.listDevices();
+      expect(result).toHaveLength(1);
+      expect(result[0].trustLevel).toBe('trusted');
+    });
+  });
+
+  describe('revokeDevice', () => {
+    it('calls DELETE /auth/devices/:id', async () => {
+      globalThis.fetch = mockFetchResponse({});
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('tok', 'ref');
+
+      await client.revokeDevice('device-xyz');
+
+      const [url, opts] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+      expect(url).toBe('http://localhost:4003/api/auth/devices/device-xyz');
+      expect(opts.method).toBe('DELETE');
+    });
+  });
+
+  // ── Phase 5B: Admin security ──────────────────────
+
+  describe('getSecurityOverview', () => {
+    it('calls GET /auth/security/overview', async () => {
+      const overview = {
+        totalUsers: 100,
+        mfaAdoptionPercent: 42.5,
+        providerDistribution: { google: 60, microsoft: 30, password: 10 },
+        activeSessions: 250,
+        suspiciousEvents24h: 3,
+      };
+      globalThis.fetch = mockFetchResponse(overview);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('admin-tok', 'admin-ref');
+
+      const result = await client.getSecurityOverview();
+      expect(result.totalUsers).toBe(100);
+      expect(result.mfaAdoptionPercent).toBe(42.5);
+    });
+  });
+
+  describe('unlockUser', () => {
+    it('calls POST /auth/users/:id/unlock', async () => {
+      globalThis.fetch = mockFetchResponse({});
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('admin-tok', 'admin-ref');
+
+      await client.unlockUser('user-locked-123');
+
+      const [url, opts] = (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0];
+      expect(url).toBe('http://localhost:4003/api/auth/users/user-locked-123/unlock');
+      expect(opts.method).toBe('POST');
+    });
+  });
+
+  describe('cancelDeletion', () => {
+    it('calls POST /auth/account/cancel-deletion', async () => {
+      globalThis.fetch = mockFetchResponse({ message: 'Deletion cancelled' });
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+      client.setTokens('tok', 'ref');
+
+      const result = await client.cancelDeletion();
+      expect(result.message).toBe('Deletion cancelled');
+    });
+  });
+
+  // ── login() MFA flow ──────────────────────────────
+
+  describe('login with MFA challenge', () => {
+    it('returns MfaLoginResult and does not store tokens', async () => {
+      const mfaResponse = {
+        mfaRequired: true,
+        mfaChallenge: 'login-challenge',
+        methods: ['totp', 'recovery'],
+      };
+      globalThis.fetch = mockFetchResponse(mfaResponse);
+
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+
+      const result = await client.login('user@test.com', 'password');
+
+      expect('mfaRequired' in result).toBe(true);
+      if ('mfaRequired' in result) {
+        expect(result.mfaChallenge).toBe('login-challenge');
+        expect(result.methods).toEqual(['totp', 'recovery']);
+      }
+      expect(client.isAuthenticated()).toBe(false);
+    });
+  });
+
+  // ── createAuthClient includes all SmartAuth methods ──
+
+  describe('client exposes all SmartAuth methods', () => {
+    it('has all phase 1C, 2D, 3, 5B methods', () => {
+      const client = createAuthClient({
+        baseUrl: 'http://localhost:4003/api',
+        productId: 'testapp',
+        storage,
+      });
+
+      // Phase 1C
+      expect(client.loginWithGoogle).toBeTypeOf('function');
+      expect(client.loginWithMicrosoft).toBeTypeOf('function');
+      expect(client.loginWithApple).toBeTypeOf('function');
+      expect(client.getProviders).toBeTypeOf('function');
+      expect(client.linkProvider).toBeTypeOf('function');
+      expect(client.unlinkProvider).toBeTypeOf('function');
+      // Phase 2D
+      expect(client.verifyMfa).toBeTypeOf('function');
+      expect(client.setupTotp).toBeTypeOf('function');
+      expect(client.verifyTotpSetup).toBeTypeOf('function');
+      expect(client.disableMfa).toBeTypeOf('function');
+      expect(client.getMfaStatus).toBeTypeOf('function');
+      expect(client.regenerateRecoveryCodes).toBeTypeOf('function');
+      // Phase 3
+      expect(client.getPasskeyRegisterOptions).toBeTypeOf('function');
+      expect(client.verifyPasskeyRegistration).toBeTypeOf('function');
+      expect(client.getPasskeyAuthOptions).toBeTypeOf('function');
+      expect(client.verifyPasskeyAuth).toBeTypeOf('function');
+      expect(client.listPasskeys).toBeTypeOf('function');
+      expect(client.deletePasskey).toBeTypeOf('function');
+      expect(client.listDevices).toBeTypeOf('function');
+      expect(client.trustDevice).toBeTypeOf('function');
+      expect(client.revokeDevice).toBeTypeOf('function');
+      expect(client.revokeAllDevices).toBeTypeOf('function');
+      // Phase 5B
+      expect(client.getSecurityOverview).toBeTypeOf('function');
+      expect(client.unlockUser).toBeTypeOf('function');
+      expect(client.exportAuthData).toBeTypeOf('function');
+      expect(client.cancelDeletion).toBeTypeOf('function');
+    });
+  });
+});
diff --git a/packages/auth-client/src/client.ts b/packages/auth-client/src/client.ts
index 9ba1ff58..a4d0376e 100644
--- a/packages/auth-client/src/client.ts
+++ b/packages/auth-client/src/client.ts
@@ -18,7 +18,21 @@
  * ```
  */
 
-import type { AuthClient, AuthClientConfig, AuthResult, AuthUser, TokenStorage } from './types.js';
+import type {
+  AuthClient,
+  AuthClientConfig,
+  AuthProvider,
+  AuthResult,
+  AuthUser,
+  Device,
+  LoginEventInfo,
+  MfaRequiredResult,
+  MfaStatus,
+  Passkey,
+  SecurityOverview,
+  TokenStorage,
+  TotpSetupResult,
+} from './types.js';
 
 // ── Default localStorage adapter ─────────────────────────────────
 
@@ -167,14 +181,18 @@ export function createAuthClient(config: AuthClientConfig): AuthClient {
 
   // ── Auth operations ─────────────────────────────
 
-  async function login(email: string, password: string): Promise<AuthResult> {
-    const result = await request<AuthResult>('/auth/login', 'POST', {
+  async function login(email: string, password: string): Promise<AuthResult | MfaRequiredResult> {
+    const result = await request<AuthResult | MfaRequiredResult>('/auth/login', 'POST', {
       email,
       password,
       productId,
     });
-    setTokens(result.accessToken, result.refreshToken);
-    return result;
+    if ('mfaRequired' in result && result.mfaRequired) {
+      return result;
+    }
+    const authResult = result as AuthResult;
+    setTokens(authResult.accessToken, authResult.refreshToken);
+    return authResult;
   }
 
   async function register(
@@ -245,6 +263,188 @@ export function createAuthClient(config: AuthClientConfig): AuthClient {
     });
   }
 
+  // ── OAuth / Social login (Phase 1C) ────────────────
+
+  async function loginWithOAuth(
+    provider: string,
+    idToken: string
+  ): Promise<AuthResult | MfaRequiredResult> {
+    const result = await request<AuthResult | MfaRequiredResult>(
+      `/auth/oauth/${provider}`,
+      'POST',
+      { idToken },
+      { skipAuth: true }
+    );
+    if ('mfaRequired' in result && result.mfaRequired) {
+      return result;
+    }
+    const authResult = result as AuthResult;
+    setTokens(authResult.accessToken, authResult.refreshToken);
+    return authResult;
+  }
+
+  async function loginWithGoogle(idToken: string): Promise<AuthResult | MfaRequiredResult> {
+    return loginWithOAuth('google', idToken);
+  }
+
+  async function loginWithMicrosoft(idToken: string): Promise<AuthResult | MfaRequiredResult> {
+    return loginWithOAuth('microsoft', idToken);
+  }
+
+  async function loginWithApple(idToken: string): Promise<AuthResult | MfaRequiredResult> {
+    return loginWithOAuth('apple', idToken);
+  }
+
+  // ── Provider management (Phase 1C) ─────────────────
+
+  async function getProviders(): Promise<AuthProvider[]> {
+    return request<AuthProvider[]>('/auth/providers', 'GET');
+  }
+
+  async function linkProvider(provider: string, idToken: string): Promise<void> {
+    await request<void>('/auth/providers/link', 'POST', { provider, idToken });
+  }
+
+  async function unlinkProvider(provider: string): Promise<void> {
+    await request<void>(`/auth/providers/${provider}`, 'DELETE');
+  }
+
+  // ── MFA (Phase 2D) ─────────────────────────────────
+
+  async function verifyMfa(
+    challengeToken: string,
+    code: string,
+    method: 'totp' | 'recovery'
+  ): Promise<AuthResult> {
+    const result = await request<AuthResult>('/auth/mfa/verify', 'POST', {
+      challengeToken,
+      code,
+      method,
+    });
+    setTokens(result.accessToken, result.refreshToken);
+    return result;
+  }
+
+  async function setupTotp(): Promise<TotpSetupResult> {
+    return request<TotpSetupResult>('/auth/mfa/totp/setup', 'POST');
+  }
+
+  async function verifyTotpSetup(code: string): Promise<void> {
+    await request<void>('/auth/mfa/totp/verify-setup', 'POST', { code });
+  }
+
+  async function disableMfa(): Promise<void> {
+    await request<void>('/auth/mfa/totp', 'DELETE');
+  }
+
+  async function getMfaStatus(): Promise<MfaStatus> {
+    return request<MfaStatus>('/auth/mfa/status', 'GET');
+  }
+
+  async function regenerateRecoveryCodes(): Promise<{ codes: string[] }> {
+    return request<{ codes: string[] }>('/auth/mfa/recovery/regenerate', 'POST');
+  }
+
+  // ── Passkeys (Phase 3) ─────────────────────────────
+
+  async function getPasskeyRegisterOptions(): Promise<unknown> {
+    return request<unknown>('/auth/passkeys/register/options', 'POST');
+  }
+
+  async function verifyPasskeyRegistration(response: unknown): Promise<void> {
+    await request<void>('/auth/passkeys/register/verify', 'POST', response);
+  }
+
+  async function getPasskeyAuthOptions(): Promise<unknown> {
+    return request<unknown>('/auth/passkeys/authenticate/options', 'POST', undefined, {
+      skipAuth: true,
+    });
+  }
+
+  async function verifyPasskeyAuth(response: unknown): Promise<AuthResult> {
+    const result = await request<AuthResult>(
+      '/auth/passkeys/authenticate/verify',
+      'POST',
+      response,
+      { skipAuth: true }
+    );
+    setTokens(result.accessToken, result.refreshToken);
+    return result;
+  }
+
+  async function listPasskeys(): Promise<Passkey[]> {
+    return request<Passkey[]>('/auth/passkeys', 'GET');
+  }
+
+  async function deletePasskey(id: string): Promise<void> {
+    await request<void>(`/auth/passkeys/${id}`, 'DELETE');
+  }
+
+  // ── Devices (Phase 3) ──────────────────────────────
+
+  async function listDevices(): Promise<Device[]> {
+    return request<Device[]>('/auth/devices', 'GET');
+  }
+
+  async function trustDevice(): Promise<void> {
+    await request<void>('/auth/devices/trust', 'POST');
+  }
+
+  async function revokeDevice(deviceId: string): Promise<void> {
+    await request<void>(`/auth/devices/${deviceId}`, 'DELETE');
+  }
+
+  async function revokeAllDevices(): Promise<void> {
+    await request<void>('/auth/devices', 'DELETE');
+  }
+
+  // ── Admin security (Phase 5B) ──────────────────────
+
+  async function getSecurityOverview(): Promise<SecurityOverview> {
+    return request<SecurityOverview>('/auth/security/overview', 'GET');
+  }
+
+  async function unlockUser(userId: string): Promise<void> {
+    await request<void>(`/auth/users/${userId}/unlock`, 'POST');
+  }
+
+  async function exportAuthData(): Promise<unknown> {
+    return request<unknown>('/auth/export', 'GET');
+  }
+
+  async function cancelDeletion(): Promise<{ message: string }> {
+    return request<{ message: string }>('/auth/account/cancel-deletion', 'POST');
+  }
+
+  // ── Step-up auth ────────────────────────────────────
+
+  async function stepUp(method: string, credential: string): Promise<{ stepUpToken: string }> {
+    return request<{ stepUpToken: string }>('/auth/step-up', 'POST', { method, credential });
+  }
+
+  // ── Login history ───────────────────────────────────
+
+  async function getLoginHistory(limit = 50): Promise<LoginEventInfo[]> {
+    return request<LoginEventInfo[]>(`/auth/login-events/me?limit=${limit}`, 'GET');
+  }
+
+  // ── Admin security ──────────────────────────────────
+
+  async function getAdminLoginEvents(opts?: {
+    suspicious?: boolean;
+    limit?: number;
+  }): Promise<LoginEventInfo[]> {
+    const params = new URLSearchParams();
+    if (opts?.suspicious) params.set('suspicious', 'true');
+    if (opts?.limit) params.set('limit', String(opts.limit));
+    const qs = params.toString();
+    return request<LoginEventInfo[]>(`/auth/login-events${qs ? `?${qs}` : ''}`, 'GET');
+  }
+
+  async function getAdminDevices(userId: string): Promise<Device[]> {
+    return request<Device[]>(`/auth/devices/user/${userId}`, 'GET');
+  }
+
   return {
     getAccessToken,
     getRefreshToken,
@@ -261,5 +461,44 @@ export function createAuthClient(config: AuthClientConfig): AuthClient {
     deleteAccount,
     verifyEmail,
     resendVerification,
+    // OAuth / Social login (Phase 1C)
+    loginWithGoogle,
+    loginWithMicrosoft,
+    loginWithApple,
+    // Provider management (Phase 1C)
+    getProviders,
+    linkProvider,
+    unlinkProvider,
+    // MFA (Phase 2D)
+    verifyMfa,
+    setupTotp,
+    verifyTotpSetup,
+    disableMfa,
+    getMfaStatus,
+    regenerateRecoveryCodes,
+    // Passkeys (Phase 3)
+    getPasskeyRegisterOptions,
+    verifyPasskeyRegistration,
+    getPasskeyAuthOptions,
+    verifyPasskeyAuth,
+    listPasskeys,
+    deletePasskey,
+    // Devices (Phase 3)
+    listDevices,
+    trustDevice,
+    revokeDevice,
+    revokeAllDevices,
+    // Admin security (Phase 5B)
+    getSecurityOverview,
+    unlockUser,
+    exportAuthData,
+    cancelDeletion,
+    // Step-up auth
+    stepUp,
+    // Login history
+    getLoginHistory,
+    // Admin queries
+    getAdminLoginEvents,
+    getAdminDevices,
   };
 }
diff --git a/packages/auth-client/src/index.ts b/packages/auth-client/src/index.ts
index 8e46b225..9592e2ed 100644
--- a/packages/auth-client/src/index.ts
+++ b/packages/auth-client/src/index.ts
@@ -1,2 +1,16 @@
 export { createAuthClient } from './client.js';
-export type { AuthClient, AuthClientConfig, AuthResult, AuthUser, TokenStorage } from './types.js';
+export type {
+  AuthClient,
+  AuthClientConfig,
+  AuthProvider,
+  AuthResult,
+  AuthUser,
+  Device,
+  LoginEventInfo,
+  MfaRequiredResult,
+  MfaStatus,
+  Passkey,
+  SecurityOverview,
+  TokenStorage,
+  TotpSetupResult,
+} from './types.js';
diff --git a/packages/auth-client/src/types.ts b/packages/auth-client/src/types.ts
index 20391b48..d26b3168 100644
--- a/packages/auth-client/src/types.ts
+++ b/packages/auth-client/src/types.ts
@@ -32,6 +32,10 @@ export interface AuthUser {
   displayName: string;
   role: string;
   plan: string;
+  mfaEnabled?: boolean;
+  mfaMethods?: string[];
+  providers?: string[];
+  products?: string[];
 }
 
 export interface AuthResult {
@@ -40,6 +44,70 @@ export interface AuthResult {
   user: AuthUser;
 }
 
+export interface MfaRequiredResult {
+  mfaRequired: true;
+  mfaChallenge: string;
+  methods: string[];
+}
+
+export interface TotpSetupResult {
+  otpauthUri: string;
+  qrDataUrl: string;
+  recoveryCodes: string[];
+}
+
+export interface MfaStatus {
+  mfaEnabled: boolean;
+  methods: string[];
+  recoveryCodesRemaining: number;
+}
+
+export interface AuthProvider {
+  provider: string;
+  email: string;
+  linkedAt: string;
+  lastUsedAt: string | null;
+}
+
+export interface Passkey {
+  id: string;
+  friendlyName: string;
+  deviceType: 'platform' | 'cross-platform';
+  backedUp: boolean;
+  lastUsedAt: string | null;
+  createdAt: string;
+}
+
+export interface Device {
+  id: string;
+  name: string;
+  platform: string;
+  trustLevel: 'trusted' | 'remembered' | 'unknown';
+  trustExpiresAt: string | null;
+  lastIp: string;
+  lastLoginAt: string;
+  createdAt: string;
+}
+
+export interface LoginEventInfo {
+  id: string;
+  eventType: string;
+  method: string;
+  ip: string;
+  userAgent: string;
+  riskScore: number;
+  riskFactors: string[];
+  createdAt: string;
+}
+
+export interface SecurityOverview {
+  totalUsers: number;
+  mfaAdoptionPercent: number;
+  providerDistribution: Record<string, number>;
+  activeSessions: number;
+  suspiciousEvents24h: number;
+}
+
 export interface AuthClient {
   // ── Token management ────────────────────────────
   getAccessToken(): string | null;
@@ -49,11 +117,56 @@ export interface AuthClient {
   isAuthenticated(): boolean;
 
   // ── Auth operations ─────────────────────────────
-  login(email: string, password: string): Promise<AuthResult>;
+  login(email: string, password: string): Promise<AuthResult | MfaRequiredResult>;
   register(email: string, password: string, displayName: string): Promise<AuthResult>;
   getMe(): Promise<AuthUser>;
   refreshAccessToken(): Promise<boolean>;
 
+  // ── OAuth / Social login ────────────────────────
+  loginWithGoogle(idToken: string): Promise<AuthResult | MfaRequiredResult>;
+  loginWithMicrosoft(idToken: string): Promise<AuthResult | MfaRequiredResult>;
+  loginWithApple(idToken: string): Promise<AuthResult | MfaRequiredResult>;
+
+  // ── Provider management ─────────────────────────
+  getProviders(): Promise<AuthProvider[]>;
+  linkProvider(provider: string, idToken: string): Promise<void>;
+  unlinkProvider(provider: string): Promise<void>;
+
+  // ── MFA ─────────────────────────────────────────
+  verifyMfa(challengeToken: string, code: string, method: 'totp' | 'recovery'): Promise<AuthResult>;
+  setupTotp(): Promise<TotpSetupResult>;
+  verifyTotpSetup(code: string): Promise<void>;
+  disableMfa(): Promise<void>;
+  getMfaStatus(): Promise<MfaStatus>;
+  regenerateRecoveryCodes(): Promise<{ codes: string[] }>;
+
+  // ── Passkeys (WebAuthn) ─────────────────────────
+  getPasskeyRegisterOptions(): Promise<unknown>;
+  verifyPasskeyRegistration(response: unknown): Promise<void>;
+  getPasskeyAuthOptions(): Promise<unknown>;
+  verifyPasskeyAuth(response: unknown): Promise<AuthResult>;
+  listPasskeys(): Promise<Passkey[]>;
+  deletePasskey(id: string): Promise<void>;
+
+  // ── Devices ─────────────────────────────────────
+  listDevices(): Promise<Device[]>;
+  trustDevice(): Promise<void>;
+  revokeDevice(deviceId: string): Promise<void>;
+  revokeAllDevices(): Promise<void>;
+
+  // ── Step-up auth ────────────────────────────────
+  stepUp(method: string, credential: string): Promise<{ stepUpToken: string }>;
+
+  // ── Login history ───────────────────────────────
+  getLoginHistory(limit?: number): Promise<LoginEventInfo[]>;
+
+  // ── Admin security ──────────────────────────────
+  getSecurityOverview(): Promise<SecurityOverview>;
+  unlockUser(userId: string): Promise<void>;
+  getAdminLoginEvents(opts?: { suspicious?: boolean; limit?: number }): Promise<LoginEventInfo[]>;
+  getAdminDevices(userId: string): Promise<Device[]>;
+  exportAuthData(): Promise<unknown>;
+
   // ── Password management ─────────────────────────
   forgotPassword(email: string): Promise<{ message: string }>;
   resetPassword(token: string, newPassword: string): Promise<{ message: string }>;
@@ -61,6 +174,7 @@ export interface AuthClient {
 
   // ── Account management ──────────────────────────
   deleteAccount(password: string): Promise<{ message: string }>;
+  cancelDeletion(): Promise<{ message: string }>;
 
   // ── Email verification ──────────────────────────
   verifyEmail(token: string): Promise<{ message: string }>;
diff --git a/packages/auth-ui/package.json b/packages/auth-ui/package.json
new file mode 100644
index 00000000..afbb9362
--- /dev/null
+++ b/packages/auth-ui/package.json
@@ -0,0 +1,33 @@
+{
+  "name": "@bytelyst/auth-ui",
+  "version": "0.1.0",
+  "type": "module",
+  "description": "Shared auth UI components for SmartAuth (LoginForm, MfaChallenge, SocialButtons)",
+  "exports": {
+    ".": {
+      "import": "./dist/index.js",
+      "types": "./dist/index.d.ts"
+    }
+  },
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "files": [
+    "dist"
+  ],
+  "scripts": {
+    "build": "tsc",
+    "test": "vitest run"
+  },
+  "peerDependencies": {
+    "react": ">=18.0.0",
+    "react-dom": ">=18.0.0"
+  },
+  "devDependencies": {
+    "@testing-library/react": "^16.3.2",
+    "@types/react": "^19.2.14",
+    "@types/react-dom": "^19.2.3",
+    "happy-dom": "^18.0.1",
+    "react": "^19.2.4",
+    "react-dom": "^19.2.4"
+  }
+}
diff --git a/packages/auth-ui/src/LoginForm.tsx b/packages/auth-ui/src/LoginForm.tsx
new file mode 100644
index 00000000..d4fbbc87
--- /dev/null
+++ b/packages/auth-ui/src/LoginForm.tsx
@@ -0,0 +1,116 @@
+import { useState, type FormEvent } from 'react';
+import { SocialButtons } from './SocialButtons.js';
+import type { LoginFormProps } from './types.js';
+
+/**
+ * Email/password login form with optional social login buttons.
+ * Styled via CSS custom properties (inherits --bl-* from host app).
+ */
+export function LoginForm({
+  onSubmit,
+  providers,
+  onSocialLogin,
+  isLoading = false,
+  error,
+  className,
+}: LoginFormProps) {
+  const [email, setEmail] = useState('');
+  const [password, setPassword] = useState('');
+
+  function handleSubmit(e: FormEvent) {
+    e.preventDefault();
+    onSubmit(email, password);
+  }
+
+  return (
+    <div className={className} data-testid="bl-login-form">
+      <form
+        onSubmit={handleSubmit}
+        style={{ display: 'flex', flexDirection: 'column', gap: '12px' }}
+      >
+        <input
+          type="email"
+          placeholder="Email"
+          value={email}
+          onChange={e => setEmail(e.target.value)}
+          required
+          disabled={isLoading}
+          data-testid="bl-login-email"
+          style={{
+            padding: '10px 12px',
+            border: '1px solid var(--bl-border, #ccc)',
+            borderRadius: 'var(--bl-radius, 6px)',
+            fontSize: '14px',
+          }}
+        />
+        <input
+          type="password"
+          placeholder="Password"
+          value={password}
+          onChange={e => setPassword(e.target.value)}
+          required
+          disabled={isLoading}
+          data-testid="bl-login-password"
+          style={{
+            padding: '10px 12px',
+            border: '1px solid var(--bl-border, #ccc)',
+            borderRadius: 'var(--bl-radius, 6px)',
+            fontSize: '14px',
+          }}
+        />
+
+        {error && (
+          <div
+            data-testid="bl-login-error"
+            style={{ color: 'var(--bl-error, #dc3545)', fontSize: '13px' }}
+          >
+            {error}
+          </div>
+        )}
+
+        <button
+          type="submit"
+          disabled={isLoading}
+          data-testid="bl-login-submit"
+          style={{
+            padding: '10px 16px',
+            border: 'none',
+            borderRadius: 'var(--bl-radius, 6px)',
+            background: 'var(--bl-primary, #0066ff)',
+            color: '#fff',
+            cursor: isLoading ? 'not-allowed' : 'pointer',
+            fontSize: '14px',
+            fontWeight: 600,
+            opacity: isLoading ? 0.6 : 1,
+          }}
+        >
+          {isLoading ? 'Signing in...' : 'Sign in'}
+        </button>
+      </form>
+
+      {providers && providers.length > 0 && onSocialLogin && (
+        <>
+          <div
+            style={{
+              display: 'flex',
+              alignItems: 'center',
+              gap: '12px',
+              margin: '16px 0',
+              color: 'var(--bl-muted, #999)',
+              fontSize: '13px',
+            }}
+          >
+            <hr
+              style={{ flex: 1, border: 'none', borderTop: '1px solid var(--bl-border, #eee)' }}
+            />
+            or
+            <hr
+              style={{ flex: 1, border: 'none', borderTop: '1px solid var(--bl-border, #eee)' }}
+            />
+          </div>
+          <SocialButtons providers={providers} onSelect={onSocialLogin} disabled={isLoading} />
+        </>
+      )}
+    </div>
+  );
+}
diff --git a/packages/auth-ui/src/MfaChallenge.tsx b/packages/auth-ui/src/MfaChallenge.tsx
new file mode 100644
index 00000000..289cfe03
--- /dev/null
+++ b/packages/auth-ui/src/MfaChallenge.tsx
@@ -0,0 +1,114 @@
+import { useState, type FormEvent } from 'react';
+import type { MfaChallengeProps } from './types.js';
+
+/**
+ * MFA code entry form (6-digit TOTP or recovery code).
+ * Styled via CSS custom properties (inherits --bl-* from host app).
+ */
+export function MfaChallenge({
+  onSubmit,
+  onUseRecovery,
+  methods,
+  isLoading = false,
+  error,
+  className,
+}: MfaChallengeProps) {
+  const [code, setCode] = useState('');
+
+  function handleSubmit(e: FormEvent) {
+    e.preventDefault();
+    onSubmit(code);
+  }
+
+  return (
+    <div className={className} data-testid="bl-mfa-challenge">
+      <form
+        onSubmit={handleSubmit}
+        style={{ display: 'flex', flexDirection: 'column', gap: '12px' }}
+      >
+        <div style={{ fontSize: '14px', color: 'var(--bl-text, #333)' }}>
+          Enter your authentication code
+        </div>
+
+        {methods && methods.length > 0 && (
+          <div
+            data-testid="bl-mfa-methods"
+            style={{ fontSize: '12px', color: 'var(--bl-muted, #999)' }}
+          >
+            Available methods: {methods.join(', ')}
+          </div>
+        )}
+
+        <input
+          type="text"
+          inputMode="numeric"
+          autoComplete="one-time-code"
+          placeholder="000000"
+          value={code}
+          onChange={e => setCode(e.target.value)}
+          required
+          disabled={isLoading}
+          maxLength={8}
+          data-testid="bl-mfa-code"
+          style={{
+            padding: '12px',
+            border: '1px solid var(--bl-border, #ccc)',
+            borderRadius: 'var(--bl-radius, 6px)',
+            fontSize: '24px',
+            textAlign: 'center',
+            letterSpacing: '4px',
+            fontFamily: 'monospace',
+          }}
+        />
+
+        {error && (
+          <div
+            data-testid="bl-mfa-error"
+            style={{ color: 'var(--bl-error, #dc3545)', fontSize: '13px' }}
+          >
+            {error}
+          </div>
+        )}
+
+        <button
+          type="submit"
+          disabled={isLoading || code.length < 6}
+          data-testid="bl-mfa-submit"
+          style={{
+            padding: '10px 16px',
+            border: 'none',
+            borderRadius: 'var(--bl-radius, 6px)',
+            background: 'var(--bl-primary, #0066ff)',
+            color: '#fff',
+            cursor: isLoading ? 'not-allowed' : 'pointer',
+            fontSize: '14px',
+            fontWeight: 600,
+            opacity: isLoading || code.length < 6 ? 0.6 : 1,
+          }}
+        >
+          {isLoading ? 'Verifying...' : 'Verify'}
+        </button>
+
+        {onUseRecovery && (
+          <button
+            type="button"
+            onClick={onUseRecovery}
+            disabled={isLoading}
+            data-testid="bl-mfa-recovery"
+            style={{
+              padding: '8px',
+              border: 'none',
+              background: 'transparent',
+              color: 'var(--bl-link, #0066ff)',
+              cursor: 'pointer',
+              fontSize: '13px',
+              textDecoration: 'underline',
+            }}
+          >
+            Use a recovery code
+          </button>
+        )}
+      </form>
+    </div>
+  );
+}
diff --git a/packages/auth-ui/src/SocialButtons.tsx b/packages/auth-ui/src/SocialButtons.tsx
new file mode 100644
index 00000000..8e0a67aa
--- /dev/null
+++ b/packages/auth-ui/src/SocialButtons.tsx
@@ -0,0 +1,48 @@
+import type { SocialButtonsProps, SocialProvider } from './types.js';
+
+const PROVIDER_LABELS: Record<SocialProvider, string> = {
+  google: 'Google',
+  microsoft: 'Microsoft',
+  apple: 'Apple',
+};
+
+/**
+ * Renders social login buttons for the configured providers.
+ * Styled via CSS custom properties (inherits --bl-* from host app).
+ */
+export function SocialButtons({
+  providers,
+  onSelect,
+  disabled = false,
+  className,
+}: SocialButtonsProps) {
+  return (
+    <div
+      className={className}
+      style={{ display: 'flex', flexDirection: 'column', gap: '8px' }}
+      data-testid="bl-social-buttons"
+    >
+      {providers.map(provider => (
+        <button
+          key={provider}
+          type="button"
+          onClick={() => onSelect(provider)}
+          disabled={disabled}
+          data-testid={`bl-social-${provider}`}
+          style={{
+            padding: '10px 16px',
+            border: '1px solid var(--bl-border, #ccc)',
+            borderRadius: 'var(--bl-radius, 6px)',
+            background: 'var(--bl-surface, #fff)',
+            color: 'var(--bl-text, #333)',
+            cursor: disabled ? 'not-allowed' : 'pointer',
+            fontSize: '14px',
+            opacity: disabled ? 0.6 : 1,
+          }}
+        >
+          Continue with {PROVIDER_LABELS[provider]}
+        </button>
+      ))}
+    </div>
+  );
+}
diff --git a/packages/auth-ui/src/__tests__/auth-ui.test.tsx b/packages/auth-ui/src/__tests__/auth-ui.test.tsx
new file mode 100644
index 00000000..32e0f12d
--- /dev/null
+++ b/packages/auth-ui/src/__tests__/auth-ui.test.tsx
@@ -0,0 +1,154 @@
+import { describe, expect, it, vi, beforeEach } from 'vitest';
+import { render, screen, fireEvent, cleanup } from '@testing-library/react';
+import { LoginForm } from '../LoginForm.js';
+import { MfaChallenge } from '../MfaChallenge.js';
+import { SocialButtons } from '../SocialButtons.js';
+
+describe('@bytelyst/auth-ui', () => {
+  beforeEach(() => {
+    cleanup();
+  });
+
+  describe('SocialButtons', () => {
+    it('renders buttons for each provider', () => {
+      const onSelect = vi.fn();
+      render(<SocialButtons providers={['google', 'microsoft', 'apple']} onSelect={onSelect} />);
+
+      expect(screen.getByTestId('bl-social-google')).toBeDefined();
+      expect(screen.getByTestId('bl-social-microsoft')).toBeDefined();
+      expect(screen.getByTestId('bl-social-apple')).toBeDefined();
+      expect(screen.getByText('Continue with Google')).toBeDefined();
+      expect(screen.getByText('Continue with Microsoft')).toBeDefined();
+      expect(screen.getByText('Continue with Apple')).toBeDefined();
+    });
+
+    it('calls onSelect with provider when clicked', () => {
+      const onSelect = vi.fn();
+      render(<SocialButtons providers={['google']} onSelect={onSelect} />);
+
+      fireEvent.click(screen.getByTestId('bl-social-google'));
+      expect(onSelect).toHaveBeenCalledWith('google');
+    });
+
+    it('disables buttons when disabled prop is true', () => {
+      const onSelect = vi.fn();
+      render(<SocialButtons providers={['google']} onSelect={onSelect} disabled />);
+
+      const btn = screen.getByTestId('bl-social-google');
+      expect(btn.getAttribute('disabled')).toBe('');
+    });
+  });
+
+  describe('LoginForm', () => {
+    it('renders email, password, and submit button', () => {
+      const onSubmit = vi.fn();
+      render(<LoginForm onSubmit={onSubmit} />);
+
+      expect(screen.getByTestId('bl-login-email')).toBeDefined();
+      expect(screen.getByTestId('bl-login-password')).toBeDefined();
+      expect(screen.getByTestId('bl-login-submit')).toBeDefined();
+      expect(screen.getByText('Sign in')).toBeDefined();
+    });
+
+    it('calls onSubmit with email and password', () => {
+      const onSubmit = vi.fn();
+      render(<LoginForm onSubmit={onSubmit} />);
+
+      fireEvent.change(screen.getByTestId('bl-login-email'), {
+        target: { value: 'test@example.com' },
+      });
+      fireEvent.change(screen.getByTestId('bl-login-password'), {
+        target: { value: 'password123' },
+      });
+      fireEvent.submit(screen.getByTestId('bl-login-submit').closest('form')!);
+
+      expect(onSubmit).toHaveBeenCalledWith('test@example.com', 'password123');
+    });
+
+    it('displays error message', () => {
+      const onSubmit = vi.fn();
+      render(<LoginForm onSubmit={onSubmit} error="Invalid credentials" />);
+
+      expect(screen.getByTestId('bl-login-error')).toBeDefined();
+      expect(screen.getByText('Invalid credentials')).toBeDefined();
+    });
+
+    it('renders social buttons when providers are given', () => {
+      const onSubmit = vi.fn();
+      const onSocialLogin = vi.fn();
+      render(
+        <LoginForm
+          onSubmit={onSubmit}
+          providers={['google', 'apple']}
+          onSocialLogin={onSocialLogin}
+        />
+      );
+
+      expect(screen.getByTestId('bl-social-google')).toBeDefined();
+      expect(screen.getByTestId('bl-social-apple')).toBeDefined();
+
+      fireEvent.click(screen.getByTestId('bl-social-google'));
+      expect(onSocialLogin).toHaveBeenCalledWith('google');
+    });
+
+    it('shows loading state', () => {
+      const onSubmit = vi.fn();
+      render(<LoginForm onSubmit={onSubmit} isLoading />);
+
+      expect(screen.getByText('Signing in...')).toBeDefined();
+      const btn = screen.getByTestId('bl-login-submit');
+      expect(btn.getAttribute('disabled')).toBe('');
+    });
+  });
+
+  describe('MfaChallenge', () => {
+    it('renders code input and verify button', () => {
+      const onSubmit = vi.fn();
+      render(<MfaChallenge onSubmit={onSubmit} />);
+
+      expect(screen.getByTestId('bl-mfa-code')).toBeDefined();
+      expect(screen.getByTestId('bl-mfa-submit')).toBeDefined();
+      expect(screen.getByText('Verify')).toBeDefined();
+    });
+
+    it('calls onSubmit with code', () => {
+      const onSubmit = vi.fn();
+      render(<MfaChallenge onSubmit={onSubmit} />);
+
+      fireEvent.change(screen.getByTestId('bl-mfa-code'), {
+        target: { value: '123456' },
+      });
+      fireEvent.submit(screen.getByTestId('bl-mfa-submit').closest('form')!);
+
+      expect(onSubmit).toHaveBeenCalledWith('123456');
+    });
+
+    it('displays available methods', () => {
+      const onSubmit = vi.fn();
+      render(<MfaChallenge onSubmit={onSubmit} methods={['totp', 'recovery']} />);
+
+      expect(screen.getByTestId('bl-mfa-methods')).toBeDefined();
+      expect(screen.getByText('Available methods: totp, recovery')).toBeDefined();
+    });
+
+    it('shows recovery code button when handler provided', () => {
+      const onSubmit = vi.fn();
+      const onUseRecovery = vi.fn();
+      render(<MfaChallenge onSubmit={onSubmit} onUseRecovery={onUseRecovery} />);
+
+      const recoveryBtn = screen.getByTestId('bl-mfa-recovery');
+      expect(recoveryBtn).toBeDefined();
+
+      fireEvent.click(recoveryBtn);
+      expect(onUseRecovery).toHaveBeenCalledOnce();
+    });
+
+    it('displays error message', () => {
+      const onSubmit = vi.fn();
+      render(<MfaChallenge onSubmit={onSubmit} error="Invalid code" />);
+
+      expect(screen.getByTestId('bl-mfa-error')).toBeDefined();
+      expect(screen.getByText('Invalid code')).toBeDefined();
+    });
+  });
+});
diff --git a/packages/auth-ui/src/index.ts b/packages/auth-ui/src/index.ts
new file mode 100644
index 00000000..9803e793
--- /dev/null
+++ b/packages/auth-ui/src/index.ts
@@ -0,0 +1,9 @@
+export { LoginForm } from './LoginForm.js';
+export { MfaChallenge } from './MfaChallenge.js';
+export { SocialButtons } from './SocialButtons.js';
+export type {
+  LoginFormProps,
+  MfaChallengeProps,
+  SocialButtonsProps,
+  SocialProvider,
+} from './types.js';
diff --git a/packages/auth-ui/src/types.ts b/packages/auth-ui/src/types.ts
new file mode 100644
index 00000000..db3f9bd5
--- /dev/null
+++ b/packages/auth-ui/src/types.ts
@@ -0,0 +1,42 @@
+export type SocialProvider = 'google' | 'microsoft' | 'apple';
+
+export interface LoginFormProps {
+  /** Called when user submits email/password. */
+  onSubmit: (email: string, password: string) => void;
+  /** Social providers to display. */
+  providers?: SocialProvider[];
+  /** Called when user clicks a social login button. */
+  onSocialLogin?: (provider: SocialProvider) => void;
+  /** Whether the form is currently loading. */
+  isLoading?: boolean;
+  /** Error message to display. */
+  error?: string | null;
+  /** Additional CSS class for the root element. */
+  className?: string;
+}
+
+export interface MfaChallengeProps {
+  /** Called when user submits the MFA code. */
+  onSubmit: (code: string) => void;
+  /** Called when user clicks "Use recovery code". */
+  onUseRecovery?: () => void;
+  /** MFA methods available. */
+  methods?: string[];
+  /** Whether the form is currently loading. */
+  isLoading?: boolean;
+  /** Error message to display. */
+  error?: string | null;
+  /** Additional CSS class for the root element. */
+  className?: string;
+}
+
+export interface SocialButtonsProps {
+  /** Providers to display buttons for. */
+  providers: SocialProvider[];
+  /** Called when a provider button is clicked. */
+  onSelect: (provider: SocialProvider) => void;
+  /** Whether the buttons are disabled. */
+  disabled?: boolean;
+  /** Additional CSS class for the root element. */
+  className?: string;
+}
diff --git a/packages/auth-ui/tsconfig.json b/packages/auth-ui/tsconfig.json
new file mode 100644
index 00000000..4447784f
--- /dev/null
+++ b/packages/auth-ui/tsconfig.json
@@ -0,0 +1,11 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "outDir": "dist",
+    "rootDir": "src",
+    "lib": ["ES2022", "DOM"],
+    "jsx": "react-jsx"
+  },
+  "include": ["src"],
+  "exclude": ["src/**/*.test.ts", "src/**/*.test.tsx"]
+}
diff --git a/packages/auth-ui/vitest.config.ts b/packages/auth-ui/vitest.config.ts
new file mode 100644
index 00000000..a9f5456f
--- /dev/null
+++ b/packages/auth-ui/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    environment: 'happy-dom',
+  },
+});
diff --git a/packages/auth/src/__tests__/rs256.test.ts b/packages/auth/src/__tests__/rs256.test.ts
new file mode 100644
index 00000000..a96832c5
--- /dev/null
+++ b/packages/auth/src/__tests__/rs256.test.ts
@@ -0,0 +1,133 @@
+import { describe, expect, it, beforeAll, afterAll } from 'vitest';
+import { generateKeyPair } from 'jose';
+import { createJwtUtils } from '../index.js';
+
+describe('JWT RS256 support (Phase 4C)', () => {
+  const SECRET = 'test-jwt-secret-at-least-32-chars-long!!';
+  let rsaPrivateKey: string;
+  let rsaPublicKey: string;
+
+  beforeAll(async () => {
+    process.env.JWT_SECRET = SECRET;
+
+    // Generate RSA key pair for testing (extractable required for PEM export in jose v6)
+    const { privateKey, publicKey } = await generateKeyPair('RS256', { extractable: true });
+    const { exportPKCS8, exportSPKI } = await import('jose');
+    rsaPrivateKey = await exportPKCS8(privateKey);
+    rsaPublicKey = await exportSPKI(publicKey);
+  });
+
+  afterAll(() => {
+    delete process.env.JWT_SECRET;
+  });
+
+  it('signs and verifies tokens with RS256', async () => {
+    const jwt = createJwtUtils({
+      issuer: 'test-rs256',
+      algorithm: 'RS256',
+      rsaPrivateKey,
+      rsaPublicKey,
+    });
+
+    const token = await jwt.createAccessToken({
+      sub: 'user-1',
+      email: 'rs256@test.com',
+      role: 'admin',
+    });
+
+    expect(typeof token).toBe('string');
+    expect(token.split('.')).toHaveLength(3);
+
+    const payload = await jwt.verifyToken(token);
+    expect(payload).not.toBeNull();
+    expect(payload!.sub).toBe('user-1');
+    expect(payload!.email).toBe('rs256@test.com');
+    expect(payload!.type).toBe('access');
+  });
+
+  it('dual verify: RS256 verifier can fall back to HS256 tokens', async () => {
+    // Create an HS256 token (simulates old tokens during migration)
+    const hs256Jwt = createJwtUtils({ issuer: 'dual-test' });
+    const hs256Token = await hs256Jwt.createAccessToken({
+      sub: 'u-old',
+      email: 'old@test.com',
+      role: 'user',
+    });
+
+    // Verify with RS256-configured jwt (should fall back to HS256)
+    const dualJwt = createJwtUtils({
+      issuer: 'dual-test',
+      algorithm: 'RS256',
+      rsaPrivateKey,
+      rsaPublicKey,
+    });
+
+    const payload = await dualJwt.verifyToken(hs256Token);
+    expect(payload).not.toBeNull();
+    expect(payload!.sub).toBe('u-old');
+    expect(payload!.email).toBe('old@test.com');
+  });
+
+  it('RS256 token is NOT verified by HS256-only verifier with different issuer', async () => {
+    const rs256Jwt = createJwtUtils({
+      issuer: 'rs256-only',
+      algorithm: 'RS256',
+      rsaPrivateKey,
+      rsaPublicKey,
+    });
+
+    const token = await rs256Jwt.createAccessToken({
+      sub: 'u1',
+      email: 'a@b.com',
+      role: 'user',
+    });
+
+    // HS256-only verifier with different issuer should reject
+    const hs256Jwt = createJwtUtils({ issuer: 'different-issuer' });
+    const result = await hs256Jwt.verifyToken(token);
+    expect(result).toBeNull();
+  });
+
+  it('RS256 refresh token works', async () => {
+    const jwt = createJwtUtils({
+      issuer: 'test-rs256',
+      algorithm: 'RS256',
+      rsaPrivateKey,
+      rsaPublicKey,
+    });
+
+    const token = await jwt.createRefreshToken({ sub: 'user-1' });
+
+    const payload = await jwt.verifyToken(token);
+    expect(payload).not.toBeNull();
+    expect(payload!.sub).toBe('user-1');
+    expect(payload!.type).toBe('refresh');
+  });
+
+  it('throws when RS256 signing without private key', async () => {
+    const jwt = createJwtUtils({
+      issuer: 'test-no-key',
+      algorithm: 'RS256',
+      rsaPublicKey, // public only, no private
+    });
+
+    await expect(
+      jwt.createAccessToken({ sub: 'u1', email: 'a@b.com', role: 'user' })
+    ).rejects.toThrow('rsaPrivateKey is required');
+  });
+
+  it('HS256 still works as default (backward compatible)', async () => {
+    const jwt = createJwtUtils({ issuer: 'hs256-compat' });
+
+    const token = await jwt.createAccessToken({
+      sub: 'u1',
+      email: 'compat@test.com',
+      role: 'user',
+    });
+
+    const payload = await jwt.verifyToken(token);
+    expect(payload).not.toBeNull();
+    expect(payload!.sub).toBe('u1');
+    expect(payload!.email).toBe('compat@test.com');
+  });
+});
diff --git a/packages/auth/src/jwt.ts b/packages/auth/src/jwt.ts
index 4e279990..57f8bb15 100644
--- a/packages/auth/src/jwt.ts
+++ b/packages/auth/src/jwt.ts
@@ -1,12 +1,24 @@
 /**
- * JWT utilities — configurable issuer and expiry.
- * Uses jose library for standards-compliant JWT handling.
+ * JWT utilities — configurable issuer, expiry, and algorithm.
+ * Supports HS256 (symmetric, default) and RS256 (asymmetric) via jose.
+ *
+ * RS256 mode (Phase 4C SmartAuth):
+ * - Sign with RSA private key (PEM)
+ * - Verify with RSA public key (PEM) or remote JWKS URL
+ * - Dual verification: tries RS256 first, falls back to HS256 during migration
  */
 
-import { SignJWT, jwtVerify } from 'jose';
+import {
+  SignJWT,
+  jwtVerify,
+  importPKCS8,
+  importSPKI,
+  createRemoteJWKSet,
+  type CryptoKey as JoseCryptoKey,
+} from 'jose';
 import type { JwtUtils, JwtUtilsOptions, TokenPayload } from './types.js';
 
-function getSecret(): Uint8Array {
+function getHmacSecret(): Uint8Array {
   const secret = process.env.JWT_SECRET;
   if (!secret) throw new Error('JWT_SECRET must be set');
   return new TextEncoder().encode(secret);
@@ -17,47 +29,145 @@ function getSecret(): Uint8Array {
  *
  * @example
  * ```ts
- * const jwt = createJwtUtils({ issuer: "lysnrai", accessTokenExpiry: "1h" });
- * const token = await jwt.createAccessToken({ sub: "u1", email: "a@b.com", role: "admin" });
- * const payload = await jwt.verifyToken(token);
+ * // HS256 (default, backward-compatible)
+ * const jwt = createJwtUtils({ issuer: "bytelyst-platform" });
+ *
+ * // RS256 (SmartAuth Phase 4C)
+ * const jwt = createJwtUtils({
+ *   issuer: "bytelyst-platform",
+ *   algorithm: "RS256",
+ *   rsaPrivateKey: process.env.JWT_PRIVATE_KEY,
+ *   rsaPublicKey: process.env.JWT_PUBLIC_KEY,
+ * });
+ *
+ * // RS256 verify-only (product backends — no private key)
+ * const jwt = createJwtUtils({
+ *   issuer: "bytelyst-platform",
+ *   algorithm: "RS256",
+ *   jwksUrl: "https://api.bytelyst.com/auth/.well-known/jwks.json",
+ * });
  * ```
  */
 export function createJwtUtils(options: JwtUtilsOptions): JwtUtils {
-  const { issuer, accessTokenExpiry = '1h', refreshTokenExpiry = '30d' } = options;
+  const {
+    issuer,
+    accessTokenExpiry = '1h',
+    refreshTokenExpiry = '30d',
+    algorithm = 'HS256',
+    rsaPrivateKey,
+    rsaPublicKey,
+    jwksUrl,
+  } = options;
+
+  // ── Key caches ────────────────────────────────────
+
+  let _rsaPrivateKeyObj: JoseCryptoKey | null = null;
+  let _rsaPublicKeyObj: JoseCryptoKey | null = null;
+  let _jwksKeySet: ReturnType<typeof createRemoteJWKSet> | null = null;
+
+  async function getRsaPrivateKey(): Promise<JoseCryptoKey> {
+    if (_rsaPrivateKeyObj) return _rsaPrivateKeyObj;
+    if (!rsaPrivateKey) throw new Error('rsaPrivateKey is required for RS256 signing');
+    _rsaPrivateKeyObj = (await importPKCS8(rsaPrivateKey, 'RS256')) as JoseCryptoKey;
+    return _rsaPrivateKeyObj;
+  }
+
+  async function getRsaPublicKey(): Promise<JoseCryptoKey> {
+    if (_rsaPublicKeyObj) return _rsaPublicKeyObj;
+    if (!rsaPublicKey) throw new Error('rsaPublicKey is required for RS256 local verification');
+    _rsaPublicKeyObj = (await importSPKI(rsaPublicKey, 'RS256')) as JoseCryptoKey;
+    return _rsaPublicKeyObj;
+  }
+
+  function getJwksKeySet(): ReturnType<typeof createRemoteJWKSet> {
+    if (_jwksKeySet) return _jwksKeySet;
+    if (!jwksUrl) throw new Error('jwksUrl is required for remote JWKS verification');
+    _jwksKeySet = createRemoteJWKSet(new URL(jwksUrl));
+    return _jwksKeySet;
+  }
+
+  // ── Signing ───────────────────────────────────────
+
+  async function sign(claims: Record<string, unknown>, expiry: string): Promise<string> {
+    if (algorithm === 'RS256') {
+      const key = await getRsaPrivateKey();
+      return new SignJWT(claims)
+        .setProtectedHeader({ alg: 'RS256' })
+        .setIssuedAt()
+        .setExpirationTime(expiry)
+        .setIssuer(issuer)
+        .sign(key);
+    }
+    return new SignJWT(claims)
+      .setProtectedHeader({ alg: 'HS256' })
+      .setIssuedAt()
+      .setExpirationTime(expiry)
+      .setIssuer(issuer)
+      .sign(getHmacSecret());
+  }
+
+  // ── Verification (dual: RS256 first, HS256 fallback) ──
+
+  async function verifyWithRS256(token: string): Promise<TokenPayload | null> {
+    try {
+      if (jwksUrl) {
+        const keySet = getJwksKeySet();
+        const { payload } = await jwtVerify(token, keySet, { issuer });
+        return payload as unknown as TokenPayload;
+      }
+      if (rsaPublicKey) {
+        const key = await getRsaPublicKey();
+        const { payload } = await jwtVerify(token, key, { issuer });
+        return payload as unknown as TokenPayload;
+      }
+      return null;
+    } catch {
+      return null;
+    }
+  }
+
+  async function verifyWithHS256(token: string): Promise<TokenPayload | null> {
+    try {
+      const secret = getHmacSecret();
+      const { payload } = await jwtVerify(token, secret, { issuer });
+      return payload as unknown as TokenPayload;
+    } catch {
+      return null;
+    }
+  }
 
   return {
     async createAccessToken(payload) {
-      return new SignJWT({
-        ...payload,
-        productId: payload.productId || issuer,
-        type: 'access',
-      })
-        .setProtectedHeader({ alg: 'HS256' })
-        .setIssuedAt()
-        .setExpirationTime(accessTokenExpiry)
-        .setIssuer(issuer)
-        .sign(getSecret());
+      return sign(
+        {
+          ...payload,
+          productId: payload.productId || issuer,
+          type: 'access',
+        },
+        accessTokenExpiry
+      );
     },
 
     async createRefreshToken(payload) {
-      return new SignJWT({
-        sub: payload.sub,
-        productId: payload.productId || issuer,
-        type: 'refresh',
-      })
-        .setProtectedHeader({ alg: 'HS256' })
-        .setIssuedAt()
-        .setExpirationTime(refreshTokenExpiry)
-        .setIssuer(issuer)
-        .sign(getSecret());
+      return sign(
+        {
+          sub: payload.sub,
+          productId: payload.productId || issuer,
+          type: 'refresh',
+        },
+        refreshTokenExpiry
+      );
     },
 
     async verifyToken(token: string) {
+      // Dual verification: try RS256 first (if configured), then HS256 fallback
+      if (algorithm === 'RS256' || jwksUrl || rsaPublicKey) {
+        const rs256Result = await verifyWithRS256(token);
+        if (rs256Result) return rs256Result;
+      }
+      // HS256 fallback (safe during migration; removed after full RS256 rollout)
       try {
-        const { payload } = await jwtVerify(token, getSecret(), {
-          issuer,
-        });
-        return payload as unknown as TokenPayload;
+        return await verifyWithHS256(token);
       } catch {
         return null;
       }
diff --git a/packages/auth/src/types.ts b/packages/auth/src/types.ts
index dfd2daab..6455fbef 100644
--- a/packages/auth/src/types.ts
+++ b/packages/auth/src/types.ts
@@ -19,6 +19,14 @@ export interface JwtUtilsOptions {
   issuer: string;
   accessTokenExpiry?: string;
   refreshTokenExpiry?: string;
+  /** JWT signing algorithm. Default: 'HS256'. Set to 'RS256' for asymmetric. */
+  algorithm?: 'HS256' | 'RS256';
+  /** RSA private key (PEM) for RS256 signing. Required when algorithm is 'RS256'. */
+  rsaPrivateKey?: string;
+  /** RSA public key (PEM) for RS256 verification. Used when algorithm is 'RS256'. */
+  rsaPublicKey?: string;
+  /** Remote JWKS URL for RS256 verification (e.g. platform-service /.well-known/jwks.json). */
+  jwksUrl?: string;
 }
 
 export interface JwtUtils {
diff --git a/packages/react-auth/src/__tests__/smartauth.test.tsx b/packages/react-auth/src/__tests__/smartauth.test.tsx
new file mode 100644
index 00000000..104e2e70
--- /dev/null
+++ b/packages/react-auth/src/__tests__/smartauth.test.tsx
@@ -0,0 +1,338 @@
+import { describe, expect, it, vi, beforeEach } from 'vitest';
+import { render, screen, act, cleanup } from '@testing-library/react';
+import { createAuthProvider } from '../index.js';
+
+interface TestUser {
+  email: string;
+  name: string;
+  role: string;
+  [key: string]: unknown;
+}
+
+const mockFetch = vi.fn();
+globalThis.fetch = mockFetch;
+
+const store: Record<string, string> = {};
+const localStorageMock = {
+  getItem: vi.fn((key: string) => store[key] ?? null),
+  setItem: vi.fn((key: string, value: string) => {
+    store[key] = value;
+  }),
+  removeItem: vi.fn((key: string) => {
+    delete store[key];
+  }),
+  clear: vi.fn(() => {
+    for (const key of Object.keys(store)) delete store[key];
+  }),
+  length: 0,
+  key: vi.fn(),
+};
+Object.defineProperty(globalThis, 'localStorage', { value: localStorageMock });
+
+function createTestAuth(overrides?: Partial<Parameters<typeof createAuthProvider<TestUser>>[0]>) {
+  return createAuthProvider<TestUser>({
+    storagePrefix: 'sa',
+    loginEndpoint: '/auth/login',
+    mapLoginResponse: (data: unknown) => {
+      const d = data as { user: TestUser; accessToken: string; refreshToken: string };
+      return { user: d.user, accessToken: d.accessToken, refreshToken: d.refreshToken };
+    },
+    ...overrides,
+  });
+}
+
+describe('react-auth SmartAuth features', () => {
+  beforeEach(() => {
+    cleanup();
+    localStorageMock.clear();
+    vi.clearAllMocks();
+    mockFetch.mockReset();
+  });
+
+  // ── Phase 1C: loginWithGoogle ──────────────────────
+
+  it('loginWithGoogle sets user on success', async () => {
+    const apiResponse = {
+      user: { email: 'g@gmail.com', name: 'Google User', role: 'user' },
+      accessToken: 'g-at',
+      refreshToken: 'g-rt',
+    };
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      json: async () => apiResponse,
+      headers: new Headers({ 'content-type': 'application/json' }),
+      status: 200,
+    });
+
+    const { AuthProvider, useAuth } = createTestAuth();
+    let loginWithGoogleFn: (idToken: string) => Promise<boolean>;
+
+    function Component() {
+      const { loginWithGoogle, user, isAuthenticated } = useAuth();
+      loginWithGoogleFn = loginWithGoogle;
+      return (
+        <div>
+          <span data-testid="auth">{String(isAuthenticated)}</span>
+          <span data-testid="email">{user?.email ?? 'none'}</span>
+        </div>
+      );
+    }
+
+    render(
+      <AuthProvider>
+        <Component />
+      </AuthProvider>
+    );
+
+    expect(screen.getByTestId('auth').textContent).toBe('false');
+
+    let result = false;
+    await act(async () => {
+      result = await loginWithGoogleFn!('google-id-token');
+    });
+
+    expect(result).toBe(true);
+    expect(screen.getByTestId('auth').textContent).toBe('true');
+    expect(screen.getByTestId('email').textContent).toBe('g@gmail.com');
+    expect(localStorageMock.setItem).toHaveBeenCalledWith('sa_access_token', 'g-at');
+  });
+
+  it('loginWithGoogle returns false on API failure', async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: false,
+      status: 401,
+      json: async () => ({ error: 'Invalid token' }),
+      headers: new Headers({ 'content-type': 'application/json' }),
+    });
+
+    const { AuthProvider, useAuth } = createTestAuth();
+    let loginWithGoogleFn: (idToken: string) => Promise<boolean>;
+
+    function Component() {
+      const { loginWithGoogle, isAuthenticated, error } = useAuth();
+      loginWithGoogleFn = loginWithGoogle;
+      return (
+        <div>
+          <span data-testid="auth">{String(isAuthenticated)}</span>
+          <span data-testid="error">{error ?? 'none'}</span>
+        </div>
+      );
+    }
+
+    render(
+      <AuthProvider>
+        <Component />
+      </AuthProvider>
+    );
+
+    let result = true;
+    await act(async () => {
+      result = await loginWithGoogleFn!('bad-token');
+    });
+
+    expect(result).toBe(false);
+    expect(screen.getByTestId('auth').textContent).toBe('false');
+  });
+
+  // ── Phase 2D: MFA challenge flow ──────────────────
+
+  it('login triggers MFA state when mfaRequired returned', async () => {
+    const mfaResponse = {
+      mfaRequired: true,
+      mfaChallenge: 'challenge-xyz',
+      methods: ['totp'],
+    };
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      json: async () => mfaResponse,
+      headers: new Headers({ 'content-type': 'application/json' }),
+      status: 200,
+    });
+
+    const onMfaRequired = vi.fn();
+    const { AuthProvider, useAuth } = createTestAuth({ onMfaRequired });
+    let loginFn: (email: string, password: string) => Promise<boolean>;
+
+    function Component() {
+      const { login, mfaRequired, mfaChallenge, mfaMethods, isAuthenticated } = useAuth();
+      loginFn = login;
+      return (
+        <div>
+          <span data-testid="auth">{String(isAuthenticated)}</span>
+          <span data-testid="mfa">{String(mfaRequired)}</span>
+          <span data-testid="challenge">{mfaChallenge ?? 'none'}</span>
+          <span data-testid="methods">{mfaMethods.join(',') || 'none'}</span>
+        </div>
+      );
+    }
+
+    render(
+      <AuthProvider>
+        <Component />
+      </AuthProvider>
+    );
+
+    let result = true;
+    await act(async () => {
+      result = await loginFn!('user@test.com', 'pass');
+    });
+
+    // Login returns false (MFA required, not yet authenticated)
+    expect(result).toBe(false);
+    expect(screen.getByTestId('auth').textContent).toBe('false');
+    expect(screen.getByTestId('mfa').textContent).toBe('true');
+    expect(screen.getByTestId('challenge').textContent).toBe('challenge-xyz');
+    expect(screen.getByTestId('methods').textContent).toBe('totp');
+    expect(onMfaRequired).toHaveBeenCalledWith('challenge-xyz', ['totp']);
+  });
+
+  it('verifyMfa completes login after MFA challenge', async () => {
+    // Step 1: login triggers MFA
+    const mfaResponse = {
+      mfaRequired: true,
+      mfaChallenge: 'challenge-abc',
+      methods: ['totp'],
+    };
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      json: async () => mfaResponse,
+      headers: new Headers({ 'content-type': 'application/json' }),
+      status: 200,
+    });
+
+    const { AuthProvider, useAuth } = createTestAuth();
+    let loginFn: (email: string, password: string) => Promise<boolean>;
+    let verifyMfaFn: (code: string, method: 'totp' | 'recovery') => Promise<boolean>;
+
+    function Component() {
+      const { login, verifyMfa, mfaRequired, isAuthenticated, user } = useAuth();
+      loginFn = login;
+      verifyMfaFn = verifyMfa;
+      return (
+        <div>
+          <span data-testid="auth">{String(isAuthenticated)}</span>
+          <span data-testid="mfa">{String(mfaRequired)}</span>
+          <span data-testid="email">{user?.email ?? 'none'}</span>
+        </div>
+      );
+    }
+
+    render(
+      <AuthProvider>
+        <Component />
+      </AuthProvider>
+    );
+
+    await act(async () => {
+      await loginFn!('user@test.com', 'pass');
+    });
+
+    expect(screen.getByTestId('mfa').textContent).toBe('true');
+    expect(screen.getByTestId('auth').textContent).toBe('false');
+
+    // Step 2: verify MFA
+    const verifyResponse = {
+      user: { email: 'user@test.com', name: 'Test', role: 'user' },
+      accessToken: 'mfa-at',
+      refreshToken: 'mfa-rt',
+    };
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      json: async () => verifyResponse,
+      headers: new Headers({ 'content-type': 'application/json' }),
+      status: 200,
+    });
+
+    let verifyResult = false;
+    await act(async () => {
+      verifyResult = await verifyMfaFn!('123456', 'totp');
+    });
+
+    expect(verifyResult).toBe(true);
+    expect(screen.getByTestId('auth').textContent).toBe('true');
+    expect(screen.getByTestId('mfa').textContent).toBe('false');
+    expect(screen.getByTestId('email').textContent).toBe('user@test.com');
+    expect(localStorageMock.setItem).toHaveBeenCalledWith('sa_access_token', 'mfa-at');
+  });
+
+  // ── Phase 1C: Provider management ─────────────────
+
+  it('providers starts empty and exposes link/unlink', () => {
+    const { AuthProvider, useAuth } = createTestAuth();
+
+    function Component() {
+      const { providers, linkProvider, unlinkProvider, refreshProviders } = useAuth();
+      return (
+        <div>
+          <span data-testid="count">{providers.length}</span>
+          <span data-testid="hasLink">{String(typeof linkProvider === 'function')}</span>
+          <span data-testid="hasUnlink">{String(typeof unlinkProvider === 'function')}</span>
+          <span data-testid="hasRefresh">{String(typeof refreshProviders === 'function')}</span>
+        </div>
+      );
+    }
+
+    render(
+      <AuthProvider>
+        <Component />
+      </AuthProvider>
+    );
+
+    expect(screen.getByTestId('count').textContent).toBe('0');
+    expect(screen.getByTestId('hasLink').textContent).toBe('true');
+    expect(screen.getByTestId('hasUnlink').textContent).toBe('true');
+    expect(screen.getByTestId('hasRefresh').textContent).toBe('true');
+  });
+
+  // ── Logout clears SmartAuth state ─────────────────
+
+  it('logout clears providers and MFA state', async () => {
+    // Login first
+    const loginResponse = {
+      user: { email: 'a@b.com', name: 'A', role: 'user' },
+      accessToken: 'at',
+      refreshToken: 'rt',
+    };
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      json: async () => loginResponse,
+      headers: new Headers({ 'content-type': 'application/json' }),
+      status: 200,
+    });
+
+    const { AuthProvider, useAuth } = createTestAuth();
+    let loginFn: (email: string, password: string) => Promise<boolean>;
+    let logoutFn: () => void;
+
+    function Component() {
+      const { login, logout, isAuthenticated, mfaRequired } = useAuth();
+      loginFn = login;
+      logoutFn = logout;
+      return (
+        <div>
+          <span data-testid="auth">{String(isAuthenticated)}</span>
+          <span data-testid="mfa">{String(mfaRequired)}</span>
+        </div>
+      );
+    }
+
+    render(
+      <AuthProvider>
+        <Component />
+      </AuthProvider>
+    );
+
+    await act(async () => {
+      await loginFn!('a@b.com', 'pass');
+    });
+
+    expect(screen.getByTestId('auth').textContent).toBe('true');
+
+    act(() => {
+      logoutFn!();
+    });
+
+    expect(screen.getByTestId('auth').textContent).toBe('false');
+    expect(screen.getByTestId('mfa').textContent).toBe('false');
+  });
+});
diff --git a/packages/react-auth/src/auth-context.tsx b/packages/react-auth/src/auth-context.tsx
index a3c7dc6e..d513a13b 100644
--- a/packages/react-auth/src/auth-context.tsx
+++ b/packages/react-auth/src/auth-context.tsx
@@ -10,7 +10,7 @@ import {
   type ReactNode,
 } from 'react';
 import { createApiClient } from '@bytelyst/api-client';
-import type { AuthConfig, AuthContextValue, BaseUser } from './types.js';
+import type { AuthConfig, AuthContextValue, AuthProviderInfo, BaseUser } from './types.js';
 
 /**
  * Create a typed auth provider + hook for a specific user type.
@@ -51,6 +51,11 @@ export function createAuthProvider<TUser extends BaseUser = BaseUser>(config: Au
     onLoginFallback,
     onInit,
     onLogout,
+    oauthEndpoint = '/auth/oauth',
+    providersEndpoint = '/auth/providers',
+    linkProviderEndpoint = '/auth/providers/link',
+    mfaVerifyEndpoint = '/auth/mfa/verify',
+    onMfaRequired,
   } = config;
 
   const USER_KEY = `${storagePrefix}_auth_user`;
@@ -96,6 +101,10 @@ export function createAuthProvider<TUser extends BaseUser = BaseUser>(config: Au
     const [isLoading, setIsLoading] = useState(false);
     const [error, setError] = useState<string | null>(null);
     const [success, setSuccess] = useState<string | null>(null);
+    const [providers, setProviders] = useState<AuthProviderInfo[]>([]);
+    const [mfaRequired, setMfaRequired] = useState(false);
+    const [mfaMethods, setMfaMethods] = useState<string[]>([]);
+    const [mfaChallenge, setMfaChallenge] = useState<string | null>(null);
     const refreshTimerRef = useRef<ReturnType<typeof setInterval> | null>(null);
 
     const api = createApiClient({
@@ -138,12 +147,30 @@ export function createAuthProvider<TUser extends BaseUser = BaseUser>(config: Au
       };
     }, [user, refreshAccessToken, refreshIntervalMs]);
 
+    // ── MFA challenge helper ─────────────────────────
+
+    function handleMfaChallenge(data: Record<string, unknown>): boolean {
+      if (data && typeof data === 'object' && 'mfaRequired' in data && data.mfaRequired === true) {
+        const challenge = data.mfaChallenge as string;
+        const methods = data.methods as string[];
+        setMfaRequired(true);
+        setMfaChallenge(challenge);
+        setMfaMethods(methods ?? []);
+        onMfaRequired?.(challenge, methods ?? []);
+        return true;
+      }
+      return false;
+    }
+
     // ── Login ──────────────────────────────────────
 
     const login = useCallback(
       async (email: string, password: string) => {
         setIsLoading(true);
         setError(null);
+        setMfaRequired(false);
+        setMfaChallenge(null);
+        setMfaMethods([]);
         try {
           const { data, error: fetchError } = await api.safeFetch<unknown>(loginEndpoint, {
             method: 'POST',
@@ -151,6 +178,9 @@ export function createAuthProvider<TUser extends BaseUser = BaseUser>(config: Au
           });
 
           if (data && !fetchError) {
+            if (handleMfaChallenge(data as Record<string, unknown>)) {
+              return false;
+            }
             const mapped = mapLoginResponse(data);
             setUser(mapped.user);
             saveSession(mapped.user, mapped.accessToken, mapped.refreshToken);
@@ -207,11 +237,154 @@ export function createAuthProvider<TUser extends BaseUser = BaseUser>(config: Au
       [api]
     );
 
+    // ── Social login (Phase 1C) ────────────────────
+
+    const loginWithOAuth = useCallback(
+      async (provider: string, idToken: string) => {
+        setIsLoading(true);
+        setError(null);
+        setMfaRequired(false);
+        setMfaChallenge(null);
+        setMfaMethods([]);
+        try {
+          const { data, error: fetchError } = await api.safeFetch<unknown>(
+            `${oauthEndpoint}/${provider}`,
+            { method: 'POST', body: JSON.stringify({ idToken }) }
+          );
+
+          if (data && !fetchError) {
+            if (handleMfaChallenge(data as Record<string, unknown>)) {
+              return false;
+            }
+            const mapped = mapLoginResponse(data);
+            setUser(mapped.user);
+            saveSession(mapped.user, mapped.accessToken, mapped.refreshToken);
+            return true;
+          }
+
+          setError(fetchError || `${provider} login failed`);
+          return false;
+        } finally {
+          setIsLoading(false);
+        }
+      },
+      [api]
+    );
+
+    const loginWithGoogle = useCallback(
+      (idToken: string) => loginWithOAuth('google', idToken),
+      [loginWithOAuth]
+    );
+
+    const loginWithMicrosoft = useCallback(
+      (idToken: string) => loginWithOAuth('microsoft', idToken),
+      [loginWithOAuth]
+    );
+
+    const loginWithApple = useCallback(
+      (idToken: string) => loginWithOAuth('apple', idToken),
+      [loginWithOAuth]
+    );
+
+    // ── Provider management (Phase 1C) ────────────
+
+    const refreshProviders = useCallback(async () => {
+      try {
+        const data = await api.fetch<AuthProviderInfo[]>(providersEndpoint, { method: 'GET' });
+        setProviders(data);
+      } catch {
+        // non-fatal — providers list is supplementary
+      }
+    }, [api]);
+
+    const linkProvider = useCallback(
+      async (provider: string, idToken: string) => {
+        setIsLoading(true);
+        setError(null);
+        try {
+          const { error: fetchError } = await api.safeFetch<void>(linkProviderEndpoint, {
+            method: 'POST',
+            body: JSON.stringify({ provider, idToken }),
+          });
+          if (fetchError) {
+            setError(fetchError);
+            return false;
+          }
+          await refreshProviders();
+          return true;
+        } finally {
+          setIsLoading(false);
+        }
+      },
+      [api, refreshProviders]
+    );
+
+    const unlinkProvider = useCallback(
+      async (provider: string) => {
+        setIsLoading(true);
+        setError(null);
+        try {
+          const { error: fetchError } = await api.safeFetch<void>(
+            `${providersEndpoint}/${provider}`,
+            { method: 'DELETE' }
+          );
+          if (fetchError) {
+            setError(fetchError);
+            return false;
+          }
+          await refreshProviders();
+          return true;
+        } finally {
+          setIsLoading(false);
+        }
+      },
+      [api, refreshProviders]
+    );
+
+    // ── MFA verify (Phase 2D) ─────────────────────
+
+    const verifyMfa = useCallback(
+      async (code: string, method: 'totp' | 'recovery') => {
+        if (!mfaChallenge) {
+          setError('No MFA challenge in progress');
+          return false;
+        }
+        setIsLoading(true);
+        setError(null);
+        try {
+          const { data, error: fetchError } = await api.safeFetch<unknown>(mfaVerifyEndpoint, {
+            method: 'POST',
+            body: JSON.stringify({ challengeToken: mfaChallenge, code, method }),
+          });
+
+          if (data && !fetchError) {
+            const mapped = mapLoginResponse(data);
+            setUser(mapped.user);
+            saveSession(mapped.user, mapped.accessToken, mapped.refreshToken);
+            setMfaRequired(false);
+            setMfaChallenge(null);
+            setMfaMethods([]);
+            return true;
+          }
+
+          setError(fetchError || 'MFA verification failed');
+          return false;
+        } finally {
+          setIsLoading(false);
+        }
+      },
+      [api, mfaChallenge]
+    );
+
     // ── Logout ─────────────────────────────────────
 
     const logout = useCallback(() => {
       setUser(null);
       clearSession();
+      setProviders([]);
+      setMfaRequired(false);
+      setMfaChallenge(null);
+      setMfaMethods([]);
       if (refreshTimerRef.current) clearInterval(refreshTimerRef.current);
       onLogout?.();
     }, []);
@@ -332,6 +505,20 @@ export function createAuthProvider<TUser extends BaseUser = BaseUser>(config: Au
           deleteAccount,
           updateUser,
           clearMessages,
+          // SmartAuth: Social login (Phase 1C)
+          loginWithGoogle,
+          loginWithMicrosoft,
+          loginWithApple,
+          // SmartAuth: Provider management (Phase 1C)
+          providers,
+          linkProvider,
+          unlinkProvider,
+          refreshProviders,
+          // SmartAuth: MFA state (Phase 2D)
+          mfaRequired,
+          mfaMethods,
+          mfaChallenge,
+          verifyMfa,
         }}
       >
         {children}
diff --git a/packages/react-auth/src/index.ts b/packages/react-auth/src/index.ts
index 549ad3de..424c6495 100644
--- a/packages/react-auth/src/index.ts
+++ b/packages/react-auth/src/index.ts
@@ -1,2 +1,8 @@
 export { createAuthProvider } from './auth-context.js';
-export type { BaseUser, AuthContextValue, AuthConfig, LoginResult } from './types.js';
+export type {
+  AuthProviderInfo,
+  BaseUser,
+  AuthContextValue,
+  AuthConfig,
+  LoginResult,
+} from './types.js';
diff --git a/packages/react-auth/src/types.ts b/packages/react-auth/src/types.ts
index f7287f60..13ebd6cd 100644
--- a/packages/react-auth/src/types.ts
+++ b/packages/react-auth/src/types.ts
@@ -5,6 +5,13 @@ export interface BaseUser {
   [key: string]: unknown;
 }
 
+export interface AuthProviderInfo {
+  provider: string;
+  email: string;
+  linkedAt: string;
+  lastUsedAt: string | null;
+}
+
 export interface AuthContextValue<TUser extends BaseUser = BaseUser> {
   user: TUser | null;
   isAuthenticated: boolean;
@@ -19,6 +26,23 @@ export interface AuthContextValue<TUser extends BaseUser = BaseUser> {
   deleteAccount: (password: string) => Promise<boolean>;
   updateUser: (updates: Partial<TUser>) => void;
   clearMessages: () => void;
+
+  // ── SmartAuth: Social login (Phase 1C) ────────────
+  loginWithGoogle: (idToken: string) => Promise<boolean>;
+  loginWithMicrosoft: (idToken: string) => Promise<boolean>;
+  loginWithApple: (idToken: string) => Promise<boolean>;
+
+  // ── SmartAuth: Provider management (Phase 1C) ─────
+  providers: AuthProviderInfo[];
+  linkProvider: (provider: string, idToken: string) => Promise<boolean>;
+  unlinkProvider: (provider: string) => Promise<boolean>;
+  refreshProviders: () => Promise<void>;
+
+  // ── SmartAuth: MFA state (Phase 2D) ───────────────
+  mfaRequired: boolean;
+  mfaMethods: string[];
+  mfaChallenge: string | null;
+  verifyMfa: (code: string, method: 'totp' | 'recovery') => Promise<boolean>;
 }
 
 export interface LoginResult<TUser extends BaseUser = BaseUser> {
@@ -48,4 +72,16 @@ export interface AuthConfig<TUser extends BaseUser = BaseUser> {
   /** Called once on mount to provide an initial session (e.g. from SSO cookies). Return null to fall through to localStorage. */
   onInit?: () => LoginResult<TUser> | null;
   onLogout?: () => void;
+
+  // ── SmartAuth endpoint config (Phase 1C+) ─────────
+  /** Endpoint for OAuth social login. Default: '/auth/oauth'. Provider appended as path segment. */
+  oauthEndpoint?: string;
+  /** Endpoint for listing providers. Default: '/auth/providers'. */
+  providersEndpoint?: string;
+  /** Endpoint for linking a provider. Default: '/auth/providers/link'. */
+  linkProviderEndpoint?: string;
+  /** Endpoint for MFA verification. Default: '/auth/mfa/verify'. */
+  mfaVerifyEndpoint?: string;
+  /** Callback when MFA is required after login. Receives challenge token and methods. */
+  onMfaRequired?: (challenge: string, methods: string[]) => void;
 }