diff --git a/.Jules/changelog.md b/.Jules/changelog.md
index dcc2606..fd3f3c5 100644
--- a/.Jules/changelog.md
+++ b/.Jules/changelog.md
@@ -7,6 +7,7 @@
 ## [Unreleased]
 
 ### Added
+- Inline form validation in Auth page with real-time feedback and proper ARIA accessibility support (`aria-invalid`, `aria-describedby`, `role="alert"`).
 - Dashboard skeleton loading state (`DashboardSkeleton`) to improve perceived performance during data fetch.
 - Comprehensive `EmptyState` component for Groups and Friends pages to better guide new users.
 - Toast notification system (`ToastContext`, `Toast` component) for providing non-blocking user feedback.
diff --git a/.Jules/knowledge.md b/.Jules/knowledge.md
index 3b01471..606cb38 100644
--- a/.Jules/knowledge.md
+++ b/.Jules/knowledge.md
@@ -149,6 +149,46 @@ addToast('Message', 'success|error|info');
 - Auto-dismisses after 3 seconds
 - Stacks vertically in bottom-right
 
+### Form Validation Pattern
+
+**Date:** 2026-01-01
+**Context:** Implemented in Auth.tsx
+
+```tsx
+type FormErrors = { [key: string]: string };
+const [fieldErrors, setFieldErrors] = useState<FormErrors>({});
+
+// 1. Validation Logic
+const validate = () => {
+  const newErrors: FormErrors = {};
+  if (!email) newErrors.email = 'Required';
+  setFieldErrors(newErrors);
+  return Object.keys(newErrors).length === 0;
+};
+
+// 2. Clear on type
+const clearFieldError = (field: string) => {
+  if (fieldErrors[field]) {
+    setFieldErrors(prev => ({ ...prev, [field]: undefined }));
+  }
+};
+
+// 3. Render with accessibility
+<form onSubmit={handleSubmit} noValidate>
+  <Input
+    error={fieldErrors.email}
+    onChange={(e) => {
+      setEmail(e.target.value);
+      clearFieldError('email');
+    }}
+    // Input component handles:
+    // aria-invalid={!!error}
+    // aria-describedby={`${id}-error`}
+    // Error message has id={`${id}-error`} and role="alert"
+  />
+</form>
+```
+
 ---
 
 ## Mobile Patterns
diff --git a/.Jules/todo.md b/.Jules/todo.md
index c169cac..310000d 100644
--- a/.Jules/todo.md
+++ b/.Jules/todo.md
@@ -70,13 +70,6 @@
 
 ### Web
 
-- [ ] **[ux]** Form validation with inline feedback
-  - Files: `web/pages/Auth.tsx`, `web/pages/GroupDetails.tsx`
-  - Context: Show real-time validation with error messages under inputs
-  - Impact: Users know immediately if input is valid
-  - Size: ~50 lines
-  - Added: 2026-01-01
-
 - [ ] **[style]** Consistent hover/focus states across all buttons
   - Files: `web/components/ui/Button.tsx`, usage across pages
   - Context: Ensure all buttons have proper hover + focus-visible styles
@@ -153,4 +146,9 @@
   - Files modified: `web/components/ui/EmptyState.tsx`, `web/pages/Groups.tsx`, `web/pages/Friends.tsx`
   - Impact: Users now see a polished, illustrated empty state with clear CTAs when they have no groups or friends, instead of plain text.
 
+- [x] **[ux]** Form validation with inline feedback
+  - Completed: 2026-01-01
+  - Files modified: `web/pages/Auth.tsx`
+  - Impact: Users know immediately if input is valid via inline error messages and red borders.
+
 _No tasks completed yet. Move tasks here after completion._
diff --git a/web/components/ui/Input.tsx b/web/components/ui/Input.tsx
index fe401e9..80e7fff 100644
--- a/web/components/ui/Input.tsx
+++ b/web/components/ui/Input.tsx
@@ -13,6 +13,7 @@ export const Input: React.FC<InputProps> = ({ label, error, className = '', type
   const [showPassword, setShowPassword] = useState(false);
   const generatedId = useId();
   const inputId = id || generatedId;
+  const errorId = `${inputId}-error`;
 
   const isPassword = type === 'password';
   const inputType = isPassword ? (showPassword ? 'text' : 'password') : type;
@@ -37,6 +38,8 @@ export const Input: React.FC<InputProps> = ({ label, error, className = '', type
           id={inputId}
           type={inputType}
           className={`${inputStyles} ${className}`}
+          aria-invalid={!!error}
+          aria-describedby={error ? errorId : undefined}
           {...props}
         />
         {isPassword && (
@@ -54,7 +57,7 @@ export const Input: React.FC<InputProps> = ({ label, error, className = '', type
           </button>
         )}
       </div>
-      {error && <span className="text-red-500 text-xs font-bold mt-1">{error}</span>}
+      {error && <span id={errorId} role="alert" className="text-red-500 text-xs font-bold mt-1">{error}</span>}
     </div>
   );
 };
diff --git a/web/pages/Auth.tsx b/web/pages/Auth.tsx
index e019721..4f35a28 100644
--- a/web/pages/Auth.tsx
+++ b/web/pages/Auth.tsx
@@ -16,6 +16,12 @@ import {
 } from '../services/api';
 import { signInWithGoogle } from '../services/firebase';
 
+type FormErrors = {
+  email?: string;
+  password?: string;
+  name?: string;
+};
+
 export const Auth = () => {
   const [isLogin, setIsLogin] = useState(true);
   const [email, setEmail] = useState('');
@@ -24,12 +30,36 @@ export const Auth = () => {
   const [loading, setLoading] = useState(false);
   const [googleLoading, setGoogleLoading] = useState(false);
   const [error, setError] = useState('');
+  const [fieldErrors, setFieldErrors] = useState<FormErrors>({});
 
   const { login } = useAuth();
   const { style, toggleStyle } = useTheme();
   const { addToast } = useToast();
   const navigate = useNavigate();
 
+  const validateForm = () => {
+    const newErrors: FormErrors = {};
+
+    if (!email) {
+      newErrors.email = 'Email is required';
+    } else if (!/\S+@\S+\.\S+/.test(email)) {
+      newErrors.email = 'Please enter a valid email address';
+    }
+
+    if (!password) {
+      newErrors.password = 'Password is required';
+    } else if (password.length < 6) {
+      newErrors.password = 'Password must be at least 6 characters';
+    }
+
+    if (!isLogin && !name) {
+      newErrors.name = 'Name is required';
+    }
+
+    setFieldErrors(newErrors);
+    return Object.keys(newErrors).length === 0;
+  };
+
   const handleGoogleSignIn = async () => {
     setError('');
     setGoogleLoading(true);
@@ -66,6 +96,11 @@ export const Auth = () => {
   const handleSubmit = async (e: React.FormEvent) => {
     e.preventDefault();
     setError('');
+
+    if (!validateForm()) {
+      return;
+    }
+
     setLoading(true);
 
     try {
@@ -96,6 +131,12 @@ export const Auth = () => {
     }
   };
 
+  const clearFieldError = (field: 'email' | 'password' | 'name') => {
+    if (fieldErrors[field]) {
+      setFieldErrors(prev => ({ ...prev, [field]: undefined }));
+    }
+  };
+
   const isNeo = style === THEMES.NEOBRUTALISM;
 
   return (
@@ -210,7 +251,7 @@ export const Auth = () => {
               <div className="flex-grow border-t border-gray-200 dark:border-gray-700"></div>
             </div>
 
-            <form onSubmit={handleSubmit} className="space-y-4">
+            <form onSubmit={handleSubmit} className="space-y-4" noValidate>
               <AnimatePresence mode="wait">
                 {!isLogin && (
                   <motion.div
@@ -221,8 +262,12 @@ export const Auth = () => {
                     <Input
                       placeholder="Full Name"
                       value={name}
-                      onChange={(e) => setName(e.target.value)}
+                      onChange={(e) => {
+                        setName(e.target.value);
+                        clearFieldError('name');
+                      }}
                       required
+                      error={fieldErrors.name}
                       className={isNeo ? 'rounded-none' : ''}
                     />
                   </motion.div>
@@ -233,16 +278,24 @@ export const Auth = () => {
                 type="email"
                 placeholder="Email Address"
                 value={email}
-                onChange={(e) => setEmail(e.target.value)}
+                onChange={(e) => {
+                  setEmail(e.target.value);
+                  clearFieldError('email');
+                }}
                 required
+                error={fieldErrors.email}
                 className={isNeo ? 'rounded-none' : ''}
               />
               <Input
                 type="password"
                 placeholder="Password"
                 value={password}
-                onChange={(e) => setPassword(e.target.value)}
+                onChange={(e) => {
+                  setPassword(e.target.value);
+                  clearFieldError('password');
+                }}
                 required
+                error={fieldErrors.password}
                 className={isNeo ? 'rounded-none' : ''}
               />
 
@@ -251,6 +304,7 @@ export const Auth = () => {
                   initial={{ opacity: 0, y: -10 }}
                   animate={{ opacity: 1, y: 0 }}
                   className={`p-3 text-red-600 text-sm font-medium border border-red-100 ${isNeo ? 'bg-red-100 border-2 border-black rounded-none' : 'bg-red-50 rounded-lg'}`}
+                  role="alert"
                 >
                   {error}
                 </motion.div>
@@ -268,7 +322,11 @@ export const Auth = () => {
             <div className="text-center pt-4">
               <button
                 type="button"
-                onClick={() => setIsLogin(!isLogin)}
+                onClick={() => {
+                  setIsLogin(!isLogin);
+                  setFieldErrors({});
+                  setError('');
+                }}
                 className="text-sm font-bold hover:underline opacity-70 hover:opacity-100 transition-opacity"
               >
                 {isLogin