diff --git a/public/auth/tests/behat/loginform.feature b/public/auth/tests/behat/loginform.feature
index c5107487ecd..3c7c883c5d4 100644
--- a/public/auth/tests/behat/loginform.feature
+++ b/public/auth/tests/behat/loginform.feature
@@ -43,11 +43,18 @@ Feature: Test if the login form provides the correct feedback
     Then "//img[@id='logoimage' and contains(@src, '/1.jpg')]" "xpath_element" should exist
     And "//link[@rel='shortcut icon' and contains(@href, '/2.jpg')]" "xpath_element" should exist
 
+  Scenario: Default welcome section is shown when no custom instructions are set
+    Given I am on homepage
+    Then I should see "Welcome to Moodle"
+    And I should see "You're part of a global learning community"
+
   Scenario: Add a custom welcome message
     Given the following config values are set as admin:
       | auth_instructions | Lorem ipsum dolor sit amet |
     And I am on homepage
     Then I should see "Lorem ipsum dolor sit amet"
+    And I should not see "Welcome to Moodle"
+    And I should not see "You're part of a global learning community"
 
   @javascript @accessibility
   Scenario: Show the maintenance mode message
diff --git a/public/lib/classes/output/core_renderer.php b/public/lib/classes/output/core_renderer.php
index b44d8eba650..b9fe2d771ee 100644
--- a/public/lib/classes/output/core_renderer.php
+++ b/public/lib/classes/output/core_renderer.php
@@ -4668,6 +4668,7 @@ EOD;
             true,
             ['context' => context_course::instance(SITEID), "escape" => false]
         );
+        $context->hasauthinstructions = !empty($CFG->auth_instructions);
 
         return $this->render_from_template('core/loginform', $context);
     }
diff --git a/public/theme/boost/layout/login.php b/public/theme/boost/layout/login.php
index 1a2a0c24d7c..30b9677d642 100644
--- a/public/theme/boost/layout/login.php
+++ b/public/theme/boost/layout/login.php
@@ -26,11 +26,11 @@ defined('MOODLE_INTERNAL') || die();
 
 $bodyattributes = $OUTPUT->body_attributes();
 
-// Left-panel instructions.
-$leftinstructions = get_string('loginwelcomedescription');
-if (!empty($CFG->auth_instructions)) {
-    $leftinstructions = $CFG->auth_instructions;
-}
+// Left-panel instructions. Only set when the admin has defined custom instructions;
+// the template falls back to the default welcome content when this is empty/null.
+$leftinstructions = !empty($CFG->auth_instructions)
+    ? format_text($CFG->auth_instructions, FORMAT_MOODLE, ['context' => context_system::instance()])
+    : null;
 
 $templatecontext = [
     'sitename' => format_string($SITE->shortname, true, ['context' => context_course::instance(SITEID), "escape" => false]),
diff --git a/public/theme/boost/templates/core/login_panel.mustache b/public/theme/boost/templates/core/login_panel.mustache
index 294ad49b268..e5d969e5d10 100644
--- a/public/theme/boost/templates/core/login_panel.mustache
+++ b/public/theme/boost/templates/core/login_panel.mustache
@@ -19,31 +19,39 @@
 
     Default content for the left panel of the split-screen login layout.
 
+    When leftinstructions is provided (i.e. the site has custom auth instructions configured),
+    it fully replaces the entire default welcome section (title, tagline, and stats).
+
     Example context (json):
     {
-        "leftinstructions": "<p>Your learning journey starts here. Access courses, connect with peers, and achieve your goals.</p>"
+        "leftinstructions": "<p>Welcome to our learning platform. Please log in to continue.</p>"
     }
 }}
 <div class="login-layout-left-content">
-    <h1 class="h2 mb-3">{{#str}}loginwelcometitle{{/str}}</h1>
-    <div class="mx-auto mb-4 text-start">
-        {{#leftinstructions}}
+    {{^leftinstructions}}
+        <h1 class="h2 mb-3">{{#str}}loginwelcometitle{{/str}}</h1>
+        <div class="mx-auto mb-4 text-start">
+            {{#str}}loginwelcomedescription{{/str}}
+        </div>
+        <p class="mx-auto mb-4">{{#str}}loginpaneltagline{{/str}}</p>
+        <div class="login-layout-stats" role="presentation">
+            <div class="login-layout-stat">
+                <strong class="login-layout-stat-value">{{#str}}loginstatusers_value{{/str}}</strong>
+                <span>{{#str}}loginstatusers{{/str}}</span>
+            </div>
+            <div class="login-layout-stat">
+                <strong class="login-layout-stat-value">{{#str}}loginstatsites_value{{/str}}</strong>
+                <span>{{#str}}loginstatsites{{/str}}</span>
+            </div>
+            <div class="login-layout-stat">
+                <strong class="login-layout-stat-value">{{#str}}loginstatcountries_value{{/str}}</strong>
+                <span>{{#str}}loginstatcountries{{/str}}</span>
+            </div>
+        </div>
+    {{/leftinstructions}}
+    {{#leftinstructions}}
+        <div class="mx-auto text-start">
             {{{leftinstructions}}}
-        {{/leftinstructions}}
-    </div>
-    <p class="mx-auto mb-4">{{#str}}loginpaneltagline{{/str}}</p>
-    <div class="login-layout-stats" role="presentation">
-        <div class="login-layout-stat">
-            <strong class="login-layout-stat-value">{{#str}}loginstatusers_value{{/str}}</strong>
-            <span>{{#str}}loginstatusers{{/str}}</span>
         </div>
-        <div class="login-layout-stat">
-            <strong class="login-layout-stat-value">{{#str}}loginstatsites_value{{/str}}</strong>
-            <span>{{#str}}loginstatsites{{/str}}</span>
-        </div>
-        <div class="login-layout-stat">
-            <strong class="login-layout-stat-value">{{#str}}loginstatcountries_value{{/str}}</strong>
-            <span>{{#str}}loginstatcountries{{/str}}</span>
-        </div>
-    </div>
+    {{/leftinstructions}}
 </div>