diff --git a/.replit b/.replit
index b0526f5..ae48c28 100644
--- a/.replit
+++ b/.replit
@@ -18,6 +18,10 @@ externalPort = 80
 localPort = 34047
 externalPort = 3002
 
+[[ports]]
+localPort = 36455
+externalPort = 3003
+
 [[ports]]
 localPort = 37531
 externalPort = 3001
diff --git a/client/src/components/LoginModal.tsx b/client/src/components/LoginModal.tsx
index bcd31ad..830cfb9 100644
--- a/client/src/components/LoginModal.tsx
+++ b/client/src/components/LoginModal.tsx
@@ -78,6 +78,8 @@ export default function LoginModal({ isOpen, onClose }: LoginModalProps) {
               type="text"
               value={username}
               onChange={(e) => setUsername(e.target.value)}
+              onInvalid={(e) => (e.target as HTMLInputElement).setCustomValidity('Please enter your username')}
+              onInput={(e) => (e.target as HTMLInputElement).setCustomValidity('')}
               placeholder="아이디를 입력하세요"
               required
               data-testid="input-username"
@@ -90,6 +92,8 @@ export default function LoginModal({ isOpen, onClose }: LoginModalProps) {
               type="password"
               value={password}
               onChange={(e) => setPassword(e.target.value)}
+              onInvalid={(e) => (e.target as HTMLInputElement).setCustomValidity('Please enter your password')}
+              onInput={(e) => (e.target as HTMLInputElement).setCustomValidity('')}
               placeholder="비밀번호를 입력하세요"
               required
               data-testid="input-password"
diff --git a/client/src/pages/Auctions.tsx b/client/src/pages/Auctions.tsx
index 9f77672..b9e87aa 100644
--- a/client/src/pages/Auctions.tsx
+++ b/client/src/pages/Auctions.tsx
@@ -342,6 +342,8 @@ export default function Auctions() {
                     min={parseFloat(selectedAuction.currentBid || "0") + 1}
                     value={bidForm.amount}
                     onChange={(e) => setBidForm(prev => ({ ...prev, amount: e.target.value }))}
+                    onInvalid={(e) => (e.target as HTMLInputElement).setCustomValidity('Please enter a bid amount')}
+                    onInput={(e) => (e.target as HTMLInputElement).setCustomValidity('')}
                     placeholder={`Minimum: $${(parseFloat(selectedAuction.currentBid || "0") + 1).toFixed(2)}`}
                     required
                     data-testid="input-bid-amount"
@@ -359,6 +361,8 @@ export default function Auctions() {
                     max="100"
                     value={bidForm.qualityScore}
                     onChange={(e) => setBidForm(prev => ({ ...prev, qualityScore: e.target.value }))}
+                    onInvalid={(e) => (e.target as HTMLInputElement).setCustomValidity('Please enter a quality score (1-100)')}
+                    onInput={(e) => (e.target as HTMLInputElement).setCustomValidity('')}
                     placeholder="Your self-assessed quality score"
                     required
                     data-testid="input-quality-score"
diff --git a/client/src/pages/Landing.tsx b/client/src/pages/Landing.tsx
index 27dc1aa..db0d46f 100644
--- a/client/src/pages/Landing.tsx
+++ b/client/src/pages/Landing.tsx
@@ -142,6 +142,8 @@ export default function Landing() {
               <Input
                 value={loginForm.username}
                 onChange={(e) => setLoginForm(prev => ({ ...prev, username: e.target.value }))}
+                onInvalid={(e) => (e.target as HTMLInputElement).setCustomValidity('Please enter your username')}
+                onInput={(e) => (e.target as HTMLInputElement).setCustomValidity('')}
                 placeholder="Enter username"
                 required
                 data-testid="input-username"
@@ -154,6 +156,8 @@ export default function Landing() {
                 type="password"
                 value={loginForm.password}
                 onChange={(e) => setLoginForm(prev => ({ ...prev, password: e.target.value }))}
+                onInvalid={(e) => (e.target as HTMLInputElement).setCustomValidity('Please enter your password')}
+                onInput={(e) => (e.target as HTMLInputElement).setCustomValidity('')}
                 placeholder="Enter password"
                 required
                 data-testid="input-password"
@@ -198,6 +202,8 @@ export default function Landing() {
               <Input
                 value={requestForm.name}
                 onChange={(e) => setRequestForm(prev => ({ ...prev, name: e.target.value }))}
+                onInvalid={(e) => (e.target as HTMLInputElement).setCustomValidity('Please enter outlet name')}
+                onInput={(e) => (e.target as HTMLInputElement).setCustomValidity('')}
                 placeholder="Enter outlet name"
                 required
                 data-testid="input-outlet-name"