diff --git a/frontend/src/mocks/handlers/overrides.ts b/frontend/src/mocks/handlers/overrides.ts
index 453a6be..bb151e1 100644
--- a/frontend/src/mocks/handlers/overrides.ts
+++ b/frontend/src/mocks/handlers/overrides.ts
@@ -12,8 +12,11 @@
  */
 
 import { http, HttpResponse, delay } from 'msw';
+import { generateMockToken } from '../utils/tokens';
+import { validateCredentials, setCurrentUser, currentUser } from '../data/users';
 
 const API_BASE_URL = process.env.NEXT_PUBLIC_API_BASE_URL || 'http://localhost:8000';
+const NETWORK_DELAY = 300; // ms - simulate realistic network delay
 
 /**
  * Custom handler overrides
@@ -22,17 +25,80 @@ const API_BASE_URL = process.env.NEXT_PUBLIC_API_BASE_URL || 'http://localhost:8
  * Add custom implementations here as needed.
  */
 export const overrideHandlers = [
-  // Example: Custom error simulation for testing
-  // http.post(`${API_BASE_URL}/api/v1/auth/login`, async ({ request }) => {
-  //   // Simulate rate limiting 10% of the time
-  //   if (Math.random() < 0.1) {
-  //     return HttpResponse.json(
-  //       { detail: 'Too many login attempts' },
-  //       { status: 429 }
-  //     );
-  //   }
-  //   // Otherwise, use generated handler (by not returning anything)
-  // }),
+  /**
+   * Login Override
+   * Custom handler to return proper JWT tokens and user data
+   */
+  http.post(`${API_BASE_URL}/api/v1/auth/login`, async ({ request }) => {
+    await delay(NETWORK_DELAY);
 
-  // Add your custom handlers here...
+    const body = (await request.json()) as any;
+    const user = validateCredentials(body.email, body.password);
+
+    if (!user) {
+      return HttpResponse.json({ detail: 'Incorrect email or password' }, { status: 401 });
+    }
+
+    setCurrentUser(user);
+
+    return HttpResponse.json({
+      access_token: generateMockToken('access', user.id),
+      refresh_token: generateMockToken('refresh', user.id),
+      token_type: 'bearer',
+      expires_in: 900,
+      user: user,
+    });
+  }),
+
+  /**
+   * Register Override
+   * Custom handler to return proper JWT tokens and user data
+   */
+  http.post(`${API_BASE_URL}/api/v1/auth/register`, async ({ request }) => {
+    await delay(NETWORK_DELAY);
+
+    const body = (await request.json()) as any;
+
+    const newUser = {
+      id: `new-user-${Date.now()}`,
+      email: body.email,
+      first_name: body.first_name,
+      last_name: body.last_name || null,
+      phone_number: body.phone_number || null,
+      is_active: true,
+      is_superuser: false,
+      created_at: new Date().toISOString(),
+      updated_at: new Date().toISOString(),
+      last_login: null,
+      organization_count: 0,
+    };
+
+    setCurrentUser(newUser);
+
+    return HttpResponse.json({
+      user: newUser,
+      access_token: generateMockToken('access', newUser.id),
+      refresh_token: generateMockToken('refresh', newUser.id),
+      token_type: 'bearer',
+      expires_in: 900,
+    });
+  }),
+
+  /**
+   * Refresh Token Override
+   * Custom handler to return proper JWT tokens
+   */
+  http.post(`${API_BASE_URL}/api/v1/auth/refresh`, async ({ request }) => {
+    await delay(NETWORK_DELAY);
+
+    // Use current user's ID if available, otherwise generate a generic token
+    const userId = currentUser?.id || 'refreshed-user';
+
+    return HttpResponse.json({
+      access_token: generateMockToken('access', userId),
+      refresh_token: generateMockToken('refresh', userId),
+      token_type: 'bearer',
+      expires_in: 900,
+    });
+  }),
 ];
diff --git a/frontend/src/mocks/utils/tokens.ts b/frontend/src/mocks/utils/tokens.ts
new file mode 100644
index 0000000..6056340
--- /dev/null
+++ b/frontend/src/mocks/utils/tokens.ts
@@ -0,0 +1,28 @@
+/**
+ * MSW Token Generation Utilities
+ *
+ * Helper functions for generating mock JWT tokens in demo mode.
+ * Tokens follow proper JWT format to pass client-side validation.
+ */
+
+/**
+ * Generate a mock JWT-like token for demo mode
+ * Format: header.payload.signature (3 parts separated by dots)
+ *
+ * @param type - Token type ('access' or 'refresh')
+ * @param userId - User ID to include in the token payload
+ * @returns JWT-formatted token string
+ */
+export function generateMockToken(type: 'access' | 'refresh', userId: string): string {
+  const header = btoa(JSON.stringify({ alg: 'HS256', typ: 'JWT' }));
+  const payload = btoa(
+    JSON.stringify({
+      sub: userId,
+      type: type,
+      iat: Math.floor(Date.now() / 1000),
+      exp: Math.floor(Date.now() / 1000) + (type === 'access' ? 900 : 2592000),
+    })
+  );
+  const signature = btoa(`demo-${type}-${userId}-${Date.now()}`);
+  return `${header}.${payload}.${signature}`;
+}