Mobile Users Can't Log In: Claude's Desktop-Only Flow

The problem

A fitness app lost 73% of their mobile users after launching a new login flow. Mobile users reported the login button was "broken" - they'd tap it repeatedly with no response. Support tickets flooded in: "Can't access my workouts!", "App frozen on login screen!". Analytics showed mobile users had a 91% bounce rate on the login page, while desktop worked perfectly. The company was losing $42,000/week in mobile subscriptions.

How AI created this issue

The developer had asked Claude to create a "modern login form with hover effects". Claude generated desktop-focused code with mouse-only interactions:

// Claude's desktop-only login implementation
const LoginForm = () => {
  const [showPassword, setShowPassword] = useState(false);
  
  useEffect(() => {
    // Custom dropdown using mouse events only
    const dropdown = document.querySelector('.custom-dropdown');
    dropdown.addEventListener('mouseenter', () => {
      dropdown.classList.add('open');
    });
    
    dropdown.addEventListener('mouseleave', () => {
      dropdown.classList.remove('open');
    });
    
    // Password visibility toggle with hover
    const passwordField = document.querySelector('.password-field');
    passwordField.addEventListener('mouseenter', (e) => {
      if (e.clientX > passwordField.offsetWidth - 50) {
        setShowPassword(true);
      }
    });
    
    // Submit button with custom click handling
    const submitBtn = document.querySelector('.submit-btn');
    submitBtn.onclick = (e) => {
      e.preventDefault();
      // Fancy ripple effect
      const ripple = document.createElement('span');
      ripple.className = 'ripple';
      ripple.style.left = e.clientX - e.target.offsetLeft + 'px';
      ripple.style.top = e.clientY - e.target.offsetTop + 'px';
      submitBtn.appendChild(ripple);
      
      setTimeout(() => handleSubmit(), 600); // Wait for animation
    };
  }, []);
  
  return (
    <form className="login-form">
      <div className="custom-dropdown">
        <span>Select Account Type</span>
        {/* Dropdown opens on hover only */}
      </div>
      
      <input type="password" className="password-field" />
      
      <button className="submit-btn">
        Sign In
      </button>
    </form>
  );
};

Claude used mouseenter/mouseleave events that don't exist on touch devices. The custom onclick handler prevented mobile Safari's touch handling. The hover-based UI patterns were impossible to activate on phones. Claude never mentioned touch events or mobile compatibility.

The solution

1. Touch-first event handling: Rebuilt with proper touch support:

   
   // Mobile-friendly implementation
   const LoginForm = () => {
     const handleInteraction = (callback) => {
       return {
         onClick: callback,
         onTouchEnd: (e) => {
           e.preventDefault(); // Prevent ghost clicks
           callback(e);
         }
       };
     };
     
     const handleSubmit = async (e) => {
       e.preventDefault();
       const formData = new FormData(e.target);
       
       try {
         setLoading(true);
         await login(Object.fromEntries(formData));
       } catch (error) {
         setError(error.message);
       } finally {
         setLoading(false);
       }
     };
     
     return (
       <form onSubmit={handleSubmit} className="login-form">
         <select 
           className="w-full p-3 border rounded"
           name="accountType"
           required
         >
           <option value="">Select Account Type</option>
           <option value="personal">Personal</option>
           <option value="trainer">Trainer</option>
         </select>
         
         <div className="relative">
           <input
             type={showPassword ? 'text' : 'password'}
             className="w-full p-3 border rounded pr-12"
             name="password"
             required
           />
           <button
             type="button"
             className="absolute right-3 top-3"
             {...handleInteraction(() => setShowPassword(!showPassword))}
             aria-label="Toggle password visibility"
           >
             {showPassword ? '👁️' : '👁️‍🗨️'}
           </button>
         </div>
         
         <button
           type="submit"
           className="w-full p-3 bg-blue-500 text-white rounded"
           disabled={loading}
         >
           {loading ? 'Signing in...' : 'Sign In'}
         </button>
       </form>
     );
   };

2. Native form elements: Replaced custom dropdowns with native selects that work everywhere
3. Progressive enhancement: Added touch gestures as enhancements, not requirements
4. Mobile-first CSS: Redesigned with thumb-friendly tap targets (min 44x44px)
5. Device testing lab: Set up BrowserStack for testing on real devices

The results

• Mobile login success rate jumped from 9% to 94%
• Recovered $168,000/month in mobile revenue
• Support tickets dropped 89% as mobile users could actually log in
• Mobile session duration increased 4.3x
• App store rating improved from 2.1 to 4.6 stars
• Page load time improved 2.1s by removing unnecessary animations

The team learned that AI tools typically generate code for desktop browsers since that's where developers test. They now specify "mobile-first" in all prompts and test on actual devices before deployment. Touch interaction is their default, with mouse events as the enhancement.