diff --git a/src/lib/app_components/e_app_sign_in_out.svelte b/src/lib/app_components/e_app_sign_in_out.svelte
index f52891c8..7f6a42d4 100644
--- a/src/lib/app_components/e_app_sign_in_out.svelte
+++ b/src/lib/app_components/e_app_sign_in_out.svelte
@@ -477,16 +477,18 @@
                                     user_obj = user_response; // Store the user object for later use
                                     user_id = user_obj.user_id; // Use the user_id for further API calls
                                     // person_id = user_obj.person_id_random;
+                                } else if (!user_response) {
+                                    alert('Sign in failed: No response from the server. Check your connection and try again.');
                                 } else {
-                                    alert('Failed to authenticate: ' + (user_response?.error || 'Unknown error'));
+                                    // API returns 'detail' for validation errors (FastAPI standard), 'error' for app-level errors
+                                    const reason = user_response?.detail || user_response?.error || 'Invalid User ID or Auth Key.';
+                                    alert('Sign in failed: ' + reason);
                                 }
                             })
                             .then((response) => {
                                 if (!user_id) {
-                                    // If we didn't get a user_id, return early
-                                    console.error(
-                                        'No user_id obtained from auth_ae_obj__username_password'
-                                    );
+                                    // Auth failed in the previous .then() — user has already been alerted
+                                    console.error('Auth (user_id+key): user_id not set after authentication attempt.');
                                     return;
                                 }
 
@@ -537,27 +539,17 @@
                                             trigger = true; // Set trigger to true to indicate we can now sign in
                                         } else {
                                             alert(
-                                                'Failed to load person information. No person record found for this user.'
+                                                'Sign in failed: No person record is linked to this user account. Please contact your administrator.'
                                             );
                                         }
                                     })
                                     .then(() => {
                                         // Once all promises are resolved, we can check if we have both user_id and person_id
                                         if (user_id && person_id) {
-                                            // Set the session information
-                                            // $ae_loc.person_id = person_id; // Set the person_id in the ae_loc store
-                                            // $ae_loc.person = person_obj; // Store the full person object for reference
-                                            // $ae_loc.user_id = user_id; // Set the user_id in the ae_loc store
-                                            // $ae_loc.user = user_obj; // Store the full user object for reference
-
-                                            console.log(`Successfully authenticated and loaded user and person records:
-                                user_id: ${user_id},
-                                person_id: ${person_id}
-                            `);
-                                            // window.location.reload(); // Reload to get the new session
+                                            console.log(`Successfully authenticated and loaded user and person records: user_id: ${user_id}, person_id: ${person_id}`);
                                         } else {
                                             console.error(
-                                                'Failed to authenticate and load data: missing user_id or person_id'
+                                                'Auth (user_id+key): finished but missing user_id or person_id — sign_in() will not be called.'
                                             );
                                         }
                                     });
@@ -584,16 +576,18 @@
                                     user_obj = user_response; // Store the user object for later use
                                     user_id = user_obj.user_id; // Use the user_id for further API calls
                                     // person_id = user_obj.person_id_random;
+                                } else if (!user_response) {
+                                    alert('Sign in failed: No response from the server. Check your connection and try again.');
                                 } else {
-                                    alert('Failed to authenticate: ' + (user_response?.error || 'Unknown error'));
+                                    // API returns 'detail' for validation errors (FastAPI standard), 'error' for app-level errors
+                                    const reason = user_response?.detail || user_response?.error || 'Invalid username or password.';
+                                    alert('Sign in failed: ' + reason);
                                 }
                             })
                             .then((response) => {
                                 if (!user_id) {
-                                    // If we didn't get a user_id, return early
-                                    console.error(
-                                        'No user_id obtained from auth_ae_obj__username_password'
-                                    );
+                                    // Auth failed in the previous .then() — user has already been alerted
+                                    console.error('Auth (username+password): user_id not set after authentication attempt.');
                                     return;
                                 }
 
@@ -644,27 +638,17 @@
                                             trigger = true; // Set trigger to true to indicate we can now sign in
                                         } else {
                                             alert(
-                                                'Failed to load person information. No person record found for this user.'
+                                                'Sign in failed: No person record is linked to this user account. Please contact your administrator.'
                                             );
                                         }
                                     })
                                     .then(() => {
                                         // Once all promises are resolved, we can check if we have both user_id and person_id
                                         if (user_id && person_id) {
-                                            // Set the session information
-                                            // $ae_loc.person_id = person_id; // Set the person_id in the ae_loc store
-                                            // $ae_loc.person = person_obj; // Store the full person object for reference
-                                            // $ae_loc.user_id = user_id; // Set the user_id in the ae_loc store
-                                            // $ae_loc.user = user_obj; // Store the full user object for reference
-
-                                            console.log(`Successfully authenticated and loaded user and person records:
-                                user_id: ${user_id},
-                                person_id: ${person_id}
-                            `);
-                                            // window.location.reload(); // Reload to get the new session
+                                            console.log(`Successfully authenticated and loaded user and person records: user_id: ${user_id}, person_id: ${person_id}`);
                                         } else {
                                             console.error(
-                                                'Failed to authenticate and load data: missing user_id or person_id'
+                                                'Auth (username+password): finished but missing user_id or person_id — sign_in() will not be called.'
                                             );
                                         }
                                     });