diff --git a/client/src/services/api.js b/client/src/services/api.js
index 0ec5301..9f8cf82 100644
--- a/client/src/services/api.js
+++ b/client/src/services/api.js
@@ -52,12 +52,24 @@ api.interceptors.response.use(
     if (error.response?.status === 401 || error.response?.status === 403) {
       // Check if it's a token-related error
       const errorMessage = error.response?.data?.message || '';
-      if (errorMessage.includes('token') || errorMessage.includes('expired') || error.response?.status === 401) {
-        console.warn('🔐 Token expired or invalid - logging out');
-        // Token expired or invalid - remove token and let ProtectedRoute handle navigation
+      if (errorMessage.includes('token') || errorMessage.includes('expired') || 
+          errorMessage.includes('invalid') || errorMessage.includes('required') ||
+          error.response?.status === 401) {
+        console.warn('🔐 Authentication failed:', errorMessage);
+        console.warn('🔐 Redirecting to login page');
+        
+        // Clear authentication data
         localStorage.removeItem('token');
-        // Force a state update by dispatching a custom event
+        localStorage.removeItem('user');
+        
+        // Dispatch logout event for components that need to react
         window.dispatchEvent(new CustomEvent('auth-logout'));
+        
+        // Redirect to login page
+        const currentPath = window.location.pathname;
+        if (currentPath !== '/login' && currentPath !== '/') {
+          window.location.href = '/login';
+        }
       }
     }
     return Promise.reject(error);
diff --git a/management/src/services/api.js b/management/src/services/api.js
index 58bf531..ea3658b 100644
--- a/management/src/services/api.js
+++ b/management/src/services/api.js
@@ -27,9 +27,17 @@ api.interceptors.response.use(
   (response) => response,
   (error) => {
     if (error.response?.status === 401) {
+      const errorData = error.response.data;
+      console.warn('🔐 Authentication failed:', errorData?.message || 'Unknown error');
+      
+      // Clear authentication data
       localStorage.removeItem('management_token')
       localStorage.removeItem('management_user')
-      window.location.href = '/login'
+      
+      // Check if the backend indicates we should redirect to login
+      if (errorData?.redirectToLogin !== false) {
+        window.location.href = '/login'
+      }
     }
     return Promise.reject(error)
   }
diff --git a/server/middleware/auth.js b/server/middleware/auth.js
index 0406f9b..0911faf 100644
--- a/server/middleware/auth.js
+++ b/server/middleware/auth.js
@@ -104,22 +104,51 @@ async function authenticateToken(req, res, next) {
     
     next();
   } catch (error) {
-    // Only log unexpected errors, not common JWT validation failures
+    // Log authentication errors for monitoring (but not in tests)
     if (process.env.NODE_ENV !== 'test' || error.name === 'TypeError') {
-      console.error('Token verification error:', error);
-    }
-    
-    // Handle specific JWT errors
-    if (error.name === 'TokenExpiredError') {
-      return res.status(401).json({
-        success: false,
-        message: 'Token expired'
+      console.error('🔐 Authentication error:', {
+        error: error.name,
+        message: error.message,
+        userAgent: req.headers['user-agent'],
+        ip: req.ip || req.connection.remoteAddress,
+        path: req.path
       });
     }
     
+    // Handle specific JWT errors with detailed responses
+    if (error.name === 'TokenExpiredError') {
+      return res.status(401).json({
+        success: false,
+        error: 'TOKEN_EXPIRED',
+        message: 'Token expired',
+        redirectToLogin: true
+      });
+    }
+    
+    if (error.name === 'JsonWebTokenError') {
+      return res.status(401).json({
+        success: false,
+        error: 'INVALID_TOKEN',
+        message: 'Invalid token',
+        redirectToLogin: true
+      });
+    }
+    
+    if (error.name === 'NotBeforeError') {
+      return res.status(401).json({
+        success: false,
+        error: 'TOKEN_NOT_ACTIVE',
+        message: 'Token not active',
+        redirectToLogin: true
+      });
+    }
+    
+    // Generic authentication error
     return res.status(401).json({
       success: false,
-      message: 'Invalid token'
+      error: 'AUTHENTICATION_FAILED',
+      message: 'Authentication failed',
+      redirectToLogin: true
     });
   }
 }
diff --git a/server/tests/integration/auth-security.test.js b/server/tests/integration/auth-security.test.js
new file mode 100644
index 0000000..3b7b3ae
--- /dev/null
+++ b/server/tests/integration/auth-security.test.js
@@ -0,0 +1,285 @@
+// CRITICAL: Set environment variables FIRST
+process.env.NODE_ENV = 'test';
+process.env.JWT_SECRET = 'test-jwt-secret-key-for-testing-only';
+
+const { describe, it, beforeEach, afterEach, before, after } = require('mocha');
+const { expect } = require('chai');
+const request = require('supertest');
+const jwt = require('jsonwebtoken');
+const { setupTestEnvironment, teardownTestEnvironment, cleanDatabase, createTestUser, createTestTenant } = require('../setup');
+
+describe('Authentication Integration Tests', () => {
+  let app, models, sequelize, user, tenant;
+
+  before(async () => {
+    ({ app, models, sequelize } = await setupTestEnvironment());
+  });
+
+  after(async () => {
+    await teardownTestEnvironment();
+  });
+
+  beforeEach(async () => {
+    await cleanDatabase();
+    tenant = await createTestTenant({ slug: 'test-tenant' });
+    user = await createTestUser({ 
+      username: 'testuser', 
+      role: 'admin',
+      tenant_id: tenant.id
+    });
+  });
+
+  describe('Protected Route Access', () => {
+    it('should deny access to protected route without token', async () => {
+      const response = await request(app)
+        .get('/api/users/profile')
+        .expect(401);
+
+      expect(response.body).to.deep.equal({
+        success: false,
+        message: 'Access token required'
+      });
+    });
+
+    it('should deny access with malformed authorization header', async () => {
+      const response = await request(app)
+        .get('/api/users/profile')
+        .set('Authorization', 'InvalidToken')
+        .expect(401);
+
+      expect(response.body).to.deep.equal({
+        success: false,
+        message: 'Invalid token format'
+      });
+    });
+
+    it('should deny access with expired token', async () => {
+      const expiredToken = jwt.sign(
+        { userId: user.id, username: user.username, role: user.role },
+        process.env.JWT_SECRET,
+        { expiresIn: '-1h' }
+      );
+
+      const response = await request(app)
+        .get('/api/users/profile')
+        .set('Authorization', `Bearer ${expiredToken}`)
+        .expect(401);
+
+      expect(response.body).to.deep.equal({
+        success: false,
+        error: 'TOKEN_EXPIRED',
+        message: 'Token expired',
+        redirectToLogin: true
+      });
+    });
+
+    it('should deny access with invalid token signature', async () => {
+      const invalidToken = jwt.sign(
+        { userId: user.id, username: user.username, role: user.role },
+        'wrong-secret',
+        { expiresIn: '1h' }
+      );
+
+      const response = await request(app)
+        .get('/api/users/profile')
+        .set('Authorization', `Bearer ${invalidToken}`)
+        .expect(401);
+
+      expect(response.body).to.deep.equal({
+        success: false,
+        error: 'INVALID_TOKEN',
+        message: 'Invalid token',
+        redirectToLogin: true
+      });
+    });
+
+    it('should deny access for non-existent user', async () => {
+      const fakeToken = jwt.sign(
+        { userId: 'non-existent-id', username: 'fake', role: 'admin' },
+        process.env.JWT_SECRET,
+        { expiresIn: '1h' }
+      );
+
+      const response = await request(app)
+        .get('/api/users/profile')
+        .set('Authorization', `Bearer ${fakeToken}`)
+        .expect(401);
+
+      expect(response.body).to.deep.equal({
+        success: false,
+        message: 'User not found'
+      });
+    });
+
+    it('should deny access for inactive user', async () => {
+      // Deactivate the user
+      await user.update({ is_active: false });
+
+      const validToken = jwt.sign(
+        { userId: user.id, username: user.username, role: user.role },
+        process.env.JWT_SECRET,
+        { expiresIn: '1h' }
+      );
+
+      const response = await request(app)
+        .get('/api/users/profile')
+        .set('Authorization', `Bearer ${validToken}`)
+        .expect(401);
+
+      expect(response.body).to.deep.equal({
+        success: false,
+        message: 'User account is inactive'
+      });
+    });
+
+    it('should allow access with valid token', async () => {
+      const validToken = jwt.sign(
+        { userId: user.id, username: user.username, role: user.role, tenantId: tenant.slug },
+        process.env.JWT_SECRET,
+        { expiresIn: '1h' }
+      );
+
+      const response = await request(app)
+        .get('/api/users/profile')
+        .set('Authorization', `Bearer ${validToken}`)
+        .expect(200);
+
+      expect(response.body.success).to.be.true;
+      expect(response.body.data).to.have.property('username', user.username);
+    });
+  });
+
+  describe('Role-Based Access Control', () => {
+    let adminUser, regularUser, adminToken, userToken;
+
+    beforeEach(async () => {
+      adminUser = await createTestUser({ 
+        username: 'admin', 
+        role: 'admin',
+        tenant_id: tenant.id
+      });
+      regularUser = await createTestUser({ 
+        username: 'user', 
+        role: 'user',
+        tenant_id: tenant.id
+      });
+
+      adminToken = jwt.sign(
+        { userId: adminUser.id, username: adminUser.username, role: adminUser.role, tenantId: tenant.slug },
+        process.env.JWT_SECRET,
+        { expiresIn: '1h' }
+      );
+
+      userToken = jwt.sign(
+        { userId: regularUser.id, username: regularUser.username, role: regularUser.role, tenantId: tenant.slug },
+        process.env.JWT_SECRET,
+        { expiresIn: '1h' }
+      );
+    });
+
+    it('should allow admin access to admin-only endpoints', async () => {
+      const response = await request(app)
+        .get('/api/health/metrics')
+        .set('Authorization', `Bearer ${adminToken}`)
+        .expect(200);
+
+      expect(response.body.success).to.be.true;
+    });
+
+    it('should deny regular user access to admin-only endpoints', async () => {
+      const response = await request(app)
+        .get('/api/health/metrics')
+        .set('Authorization', `Bearer ${userToken}`)
+        .expect(403);
+
+      expect(response.body).to.deep.equal({
+        success: false,
+        message: 'Insufficient permissions'
+      });
+    });
+  });
+
+  describe('Token Security Validation', () => {
+    it('should reject token with incorrect algorithm', async () => {
+      // Create token with different algorithm (if supported by library)
+      const maliciousToken = jwt.sign(
+        { userId: user.id, username: user.username, role: 'admin' },
+        process.env.JWT_SECRET,
+        { algorithm: 'none' }
+      );
+
+      const response = await request(app)
+        .get('/api/users/profile')
+        .set('Authorization', `Bearer ${maliciousToken}`)
+        .expect(401);
+
+      expect(response.body.success).to.be.false;
+      expect(response.body.error).to.equal('INVALID_TOKEN');
+    });
+
+    it('should reject tampered token payload', async () => {
+      const validToken = jwt.sign(
+        { userId: user.id, username: user.username, role: 'user' },
+        process.env.JWT_SECRET,
+        { expiresIn: '1h' }
+      );
+
+      // Tamper with the token by modifying the payload
+      const parts = validToken.split('.');
+      const tamperedPayload = Buffer.from('{"userId":"' + user.id + '","username":"' + user.username + '","role":"admin"}').toString('base64');
+      const tamperedToken = parts[0] + '.' + tamperedPayload + '.' + parts[2];
+
+      const response = await request(app)
+        .get('/api/users/profile')
+        .set('Authorization', `Bearer ${tamperedToken}`)
+        .expect(401);
+
+      expect(response.body.success).to.be.false;
+      expect(response.body.error).to.equal('INVALID_TOKEN');
+    });
+  });
+
+  describe('Tenant Context Validation', () => {
+    let otherTenant, otherUser;
+
+    beforeEach(async () => {
+      otherTenant = await createTestTenant({ slug: 'other-tenant' });
+      otherUser = await createTestUser({ 
+        username: 'otheruser', 
+        role: 'admin',
+        tenant_id: otherTenant.id
+      });
+    });
+
+    it('should set correct tenant context from JWT', async () => {
+      const validToken = jwt.sign(
+        { userId: user.id, username: user.username, role: user.role, tenantId: tenant.slug },
+        process.env.JWT_SECRET,
+        { expiresIn: '1h' }
+      );
+
+      // Make a request that would show tenant context in logs
+      const response = await request(app)
+        .get('/api/devices')
+        .set('Authorization', `Bearer ${validToken}`)
+        .expect(200);
+
+      expect(response.body.success).to.be.true;
+    });
+
+    it('should handle missing tenant context gracefully', async () => {
+      const tokenWithoutTenant = jwt.sign(
+        { userId: user.id, username: user.username, role: user.role },
+        process.env.JWT_SECRET,
+        { expiresIn: '1h' }
+      );
+
+      const response = await request(app)
+        .get('/api/users/profile')
+        .set('Authorization', `Bearer ${tokenWithoutTenant}`)
+        .expect(200);
+
+      expect(response.body.success).to.be.true;
+    });
+  });
+});
\ No newline at end of file
diff --git a/server/tests/middleware/auth.test.js b/server/tests/middleware/auth.test.js
index 0e5e4a2..31210fa 100644
--- a/server/tests/middleware/auth.test.js
+++ b/server/tests/middleware/auth.test.js
@@ -188,5 +188,179 @@ describe('Authentication Middleware', () => {
       expect(res.data.success).to.be.false;
       expect(res.data.message).to.equal('User account is inactive');
     });
+
+    it('should handle malformed JWT token', async () => {
+      const req = mockRequest({
+        headers: { authorization: 'Bearer malformed.jwt' }
+      });
+      const res = mockResponse();
+      const next = mockNext();
+
+      await authenticateToken(req, res, next);
+
+      expect(res.statusCode).to.equal(401);
+      expect(res.data.success).to.be.false;
+      expect(res.data.error).to.equal('INVALID_TOKEN');
+      expect(res.data.redirectToLogin).to.be.true;
+    });
+
+    it('should handle JWT with invalid signature', async () => {
+      const invalidToken = jwt.sign(
+        { userId: 1, username: 'test' },
+        'wrong-secret',
+        { expiresIn: '1h' }
+      );
+
+      const req = mockRequest({
+        headers: { authorization: `Bearer ${invalidToken}` }
+      });
+      const res = mockResponse();
+      const next = mockNext();
+
+      await authenticateToken(req, res, next);
+
+      expect(res.statusCode).to.equal(401);
+      expect(res.data.success).to.be.false;
+      expect(res.data.error).to.equal('INVALID_TOKEN');
+      expect(res.data.redirectToLogin).to.be.true;
+    });
+
+    it('should handle JWT not before error', async () => {
+      const futureToken = jwt.sign(
+        { userId: 1, username: 'test', nbf: Math.floor(Date.now() / 1000) + 3600 },
+        process.env.JWT_SECRET || 'test-secret',
+        { expiresIn: '1h' }
+      );
+
+      const req = mockRequest({
+        headers: { authorization: `Bearer ${futureToken}` }
+      });
+      const res = mockResponse();
+      const next = mockNext();
+
+      await authenticateToken(req, res, next);
+
+      expect(res.statusCode).to.equal(401);
+      expect(res.data.success).to.be.false;
+      expect(res.data.error).to.equal('TOKEN_NOT_ACTIVE');
+      expect(res.data.redirectToLogin).to.be.true;
+    });
+
+    it('should handle missing JWT_SECRET environment variable', async () => {
+      const originalSecret = process.env.JWT_SECRET;
+      delete process.env.JWT_SECRET;
+
+      const token = jwt.sign(
+        { userId: 1, username: 'test' },
+        'any-secret',
+        { expiresIn: '1h' }
+      );
+
+      const req = mockRequest({
+        headers: { authorization: `Bearer ${token}` }
+      });
+      const res = mockResponse();
+      const next = mockNext();
+
+      await authenticateToken(req, res, next);
+
+      expect(res.statusCode).to.equal(401);
+      expect(res.data.success).to.be.false;
+      expect(res.data.error).to.equal('AUTHENTICATION_FAILED');
+      expect(res.data.redirectToLogin).to.be.true;
+
+      // Restore original secret
+      process.env.JWT_SECRET = originalSecret;
+    });
+
+    it('should include error details for monitoring', async () => {
+      const originalEnv = process.env.NODE_ENV;
+      process.env.NODE_ENV = 'production';
+      
+      const consoleSpy = sinon.spy(console, 'error');
+
+      const req = mockRequest({
+        headers: { 
+          authorization: 'Bearer invalid.jwt.token',
+          'user-agent': 'Test Agent',
+        },
+        ip: '127.0.0.1',
+        path: '/api/test',
+        connection: { remoteAddress: '127.0.0.1' }
+      });
+      const res = mockResponse();
+      const next = mockNext();
+
+      await authenticateToken(req, res, next);
+
+      expect(consoleSpy.calledOnce).to.be.true;
+      const logCall = consoleSpy.firstCall.args;
+      expect(logCall[0]).to.equal('🔐 Authentication error:');
+      expect(logCall[1]).to.have.property('error');
+      expect(logCall[1]).to.have.property('userAgent', 'Test Agent');
+      expect(logCall[1]).to.have.property('ip', '127.0.0.1');
+      expect(logCall[1]).to.have.property('path', '/api/test');
+
+      consoleSpy.restore();
+      process.env.NODE_ENV = originalEnv;
+    });
+  });
+
+  describe('Enhanced Error Response Format', () => {
+    it('should return consistent error format for expired tokens', async () => {
+      const expiredToken = jwt.sign(
+        { userId: 1, username: 'test' },
+        process.env.JWT_SECRET || 'test-secret',
+        { expiresIn: '-1h' }
+      );
+
+      const req = mockRequest({
+        headers: { authorization: `Bearer ${expiredToken}` }
+      });
+      const res = mockResponse();
+      const next = mockNext();
+
+      await authenticateToken(req, res, next);
+
+      expect(res.statusCode).to.equal(401);
+      expect(res.data).to.deep.equal({
+        success: false,
+        error: 'TOKEN_EXPIRED',
+        message: 'Token expired',
+        redirectToLogin: true
+      });
+    });
+
+    it('should return consistent error format for invalid tokens', async () => {
+      const req = mockRequest({
+        headers: { authorization: 'Bearer invalid.jwt.token' }
+      });
+      const res = mockResponse();
+      const next = mockNext();
+
+      await authenticateToken(req, res, next);
+
+      expect(res.statusCode).to.equal(401);
+      expect(res.data).to.deep.equal({
+        success: false,
+        error: 'INVALID_TOKEN',
+        message: 'Invalid token',
+        redirectToLogin: true
+      });
+    });
+
+    it('should return consistent error format for missing tokens', async () => {
+      const req = mockRequest();
+      const res = mockResponse();
+      const next = mockNext();
+
+      await authenticateToken(req, res, next);
+
+      expect(res.statusCode).to.equal(401);
+      expect(res.data).to.deep.equal({
+        success: false,
+        message: 'Access token required'
+      });
+    });
   });
 });