diff --git a/static/index.html b/static/index.html
index d0692345..ac81c680 100644
--- a/static/index.html
+++ b/static/index.html
@@ -22,7 +22,7 @@
                 <h1>LLM Proxy Gateway</h1>
                 <p class="login-subtitle">Admin Dashboard</p>
             </div>
-            <form id="login-form" class="login-form">
+            <form id="login-form" class="login-form" onsubmit="event.preventDefault();">
                 <div class="form-group">
                     <input type="text" id="username" name="username" placeholder=" " required>
                     <label for="username">
diff --git a/static/js/api.js b/static/js/api.js
index 524f888d..81fe220b 100644
--- a/static/js/api.js
+++ b/static/js/api.js
@@ -32,6 +32,17 @@ class ApiClient {
         }
 
         if (!response.ok || !result.success) {
+            // Handle authentication errors (session expired, server restarted, etc.)
+            if (response.status === 401 || 
+                result.error === 'Session expired or invalid' || 
+                result.error === 'Not authenticated' ||
+                result.error === 'Admin access required') {
+                
+                if (window.authManager) {
+                    // Try to logout to clear local state and show login screen
+                    window.authManager.logout();
+                }
+            }
             throw new Error(result.error || `HTTP error! status: ${response.status}`);
         }