diff --git a/.upgradenotes/MDL-81960-2024061004043644.yml b/.upgradenotes/MDL-81960-2024061004043644.yml
index 964e907be25..c371a6aff54 100644
--- a/.upgradenotes/MDL-81960-2024061004043644.yml
+++ b/.upgradenotes/MDL-81960-2024061004043644.yml
@@ -2,6 +2,28 @@ issueNumber: MDL-81960
 notes:
   core:
     - message: >-
-        The `\moodle_url` class has been renamed to `\core\url` and now supports
-        autoloading. Existing uses are currently unaffected.
+        The following classes have been renamed and now support autoloading.
+        Existing classes are currently unaffected.
+
+        | Old class name | New class name |
+
+        | --- | --- |
+
+        | `\moodle_url` | `\core\url` |
+
+        | `\progress_trace` | `\core\output\progress_trace` |
+
+        | `\combined_progress_trace` | `\core\output\progress_trace\combined_progress_trace` |
+
+        | `\error_log_progress_trace` | `\core\output\progress_trace\error_log_progress_trace` |
+
+        | `\html_list_progress_trace` | `\core\output\progress_trace\html_list_progress_trace` |
+
+        | `\html_progress_trace` | `\core\output\progress_trace\html_progress_trace` |
+
+        | `\null_progress_trace` | `\core\output\progress_trace\null_progress_trace` |
+
+        | `\progress_trace_buffer` | `\core\output\progress_trace\progress_trace_buffer` |
+
+        | `\text_progress_trace` | `\core\output\progress_trace\text_progress_trace` |
       type: improved
diff --git a/lib/classes/output/progress_trace.php b/lib/classes/output/progress_trace.php
index fdd5d5ecac1..8a590b0aebc 100644
--- a/lib/classes/output/progress_trace.php
+++ b/lib/classes/output/progress_trace.php
@@ -14,6 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+namespace core\output;
+
 /**
  * Progress trace class.
  *
@@ -42,3 +44,8 @@ abstract class progress_trace {
     public function finished() {
     }
 }
+
+// Alias this class to the old name.
+// This file will be autoloaded by the legacyclasses autoload system.
+// In future all uses of this class will be corrected and the legacy references will be removed.
+class_alias(progress_trace::class, \progress_trace::class);
diff --git a/lib/classes/output/progress_trace/combined_progress_trace.php b/lib/classes/output/progress_trace/combined_progress_trace.php
index 88b34839f48..7027440a473 100644
--- a/lib/classes/output/progress_trace/combined_progress_trace.php
+++ b/lib/classes/output/progress_trace/combined_progress_trace.php
@@ -14,6 +14,10 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+namespace core\output\progress_trace;
+
+use core\output\progress_trace;
+
 /**
  * Special type of trace that can be used for redirecting to multiple other traces.
  *
@@ -21,7 +25,7 @@
  * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  * @package core
  */
-class combined_progress_trace extends progress_trace {
+class combined_progress_trace extends \progress_trace {
     /**
      * Constructs a new instance.
      *
@@ -50,3 +54,8 @@ class combined_progress_trace extends progress_trace {
         }
     }
 }
+
+// Alias this class to the old name.
+// This file will be autoloaded by the legacyclasses autoload system.
+// In future all uses of this class will be corrected and the legacy references will be removed.
+class_alias(combined_progress_trace::class, \combined_progress_trace::class);
diff --git a/lib/classes/output/progress_trace/error_log_progress_trace.php b/lib/classes/output/progress_trace/error_log_progress_trace.php
index 2715864bc4d..c3f17d87da7 100644
--- a/lib/classes/output/progress_trace/error_log_progress_trace.php
+++ b/lib/classes/output/progress_trace/error_log_progress_trace.php
@@ -14,6 +14,10 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+namespace core\output\progress_trace;
+
+use core\output\progress_trace;
+
 /**
  * This subclass of progress_trace outputs to error log.
  *
@@ -41,3 +45,8 @@ class error_log_progress_trace extends progress_trace {
         error_log($this->prefix . str_repeat('  ', $depth) . $message);
     }
 }
+
+// Alias this class to the old name.
+// This file will be autoloaded by the legacyclasses autoload system.
+// In future all uses of this class will be corrected and the legacy references will be removed.
+class_alias(error_log_progress_trace::class, \error_log_progress_trace::class);
diff --git a/lib/classes/output/progress_trace/html_list_progress_trace.php b/lib/classes/output/progress_trace/html_list_progress_trace.php
index b110ea22ae0..4c21c79a869 100644
--- a/lib/classes/output/progress_trace/html_list_progress_trace.php
+++ b/lib/classes/output/progress_trace/html_list_progress_trace.php
@@ -14,6 +14,10 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+namespace core\output\progress_trace;
+
+use core\output\progress_trace;
+
 /**
  * HTML List Progress Tree
  *
@@ -59,3 +63,8 @@ class html_list_progress_trace extends progress_trace {
         }
     }
 }
+
+// Alias this class to the old name.
+// This file will be autoloaded by the legacyclasses autoload system.
+// In future all uses of this class will be corrected and the legacy references will be removed.
+class_alias(html_list_progress_trace::class, \html_list_progress_trace::class);
diff --git a/lib/classes/output/progress_trace/html_progress_trace.php b/lib/classes/output/progress_trace/html_progress_trace.php
index d2772e0a09c..eda3587068e 100644
--- a/lib/classes/output/progress_trace/html_progress_trace.php
+++ b/lib/classes/output/progress_trace/html_progress_trace.php
@@ -14,6 +14,10 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+namespace core\output\progress_trace;
+
+use core\output\progress_trace;
+
 /**
  * This subclass of progress_trace outputs as HTML.
  *
@@ -31,3 +35,8 @@ class html_progress_trace extends progress_trace {
         flush();
     }
 }
+
+// Alias this class to the old name.
+// This file will be autoloaded by the legacyclasses autoload system.
+// In future all uses of this class will be corrected and the legacy references will be removed.
+class_alias(html_progress_trace::class, \html_progress_trace::class);
diff --git a/lib/classes/output/progress_trace/null_progress_trace.php b/lib/classes/output/progress_trace/null_progress_trace.php
index 4579b5837cb..6f9af4e60ef 100644
--- a/lib/classes/output/progress_trace/null_progress_trace.php
+++ b/lib/classes/output/progress_trace/null_progress_trace.php
@@ -14,6 +14,10 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+namespace core\output\progress_trace;
+
+use core\output\progress_trace;
+
 /**
  * This subclass of progress_trace does not ouput anything.
  *
@@ -29,3 +33,8 @@ class null_progress_trace extends progress_trace {
     ): void {
     }
 }
+
+// Alias this class to the old name.
+// This file will be autoloaded by the legacyclasses autoload system.
+// In future all uses of this class will be corrected and the legacy references will be removed.
+class_alias(null_progress_trace::class, \null_progress_trace::class);
diff --git a/lib/classes/output/progress_trace/progress_trace_buffer.php b/lib/classes/output/progress_trace/progress_trace_buffer.php
index 4bf56c1c7e9..dd9be00eb3a 100644
--- a/lib/classes/output/progress_trace/progress_trace_buffer.php
+++ b/lib/classes/output/progress_trace/progress_trace_buffer.php
@@ -14,6 +14,10 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+namespace core\output\progress_trace;
+
+use core\output\progress_trace;
+
 /**
  * Special type of trace that can be used for catching of output of other traces.
  *
@@ -21,7 +25,7 @@
  * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  * @package core
  */
-class progress_trace_buffer extends progress_trace {
+class progress_trace_buffer extends \progress_trace {
     /** @var string output buffer */
     protected string $buffer = '';
 
@@ -83,3 +87,8 @@ class progress_trace_buffer extends progress_trace {
         return $this->buffer;
     }
 }
+
+// Alias this class to the old name.
+// This file will be autoloaded by the legacyclasses autoload system.
+// In future all uses of this class will be corrected and the legacy references will be removed.
+class_alias(progress_trace_buffer::class, \progress_trace_buffer::class);
diff --git a/lib/classes/output/progress_trace/text_progress_trace.php b/lib/classes/output/progress_trace/text_progress_trace.php
index b9ed47c3962..94652ab489a 100644
--- a/lib/classes/output/progress_trace/text_progress_trace.php
+++ b/lib/classes/output/progress_trace/text_progress_trace.php
@@ -14,6 +14,10 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+namespace core\output\progress_trace;
+
+use core\output\progress_trace;
+
 /**
  * This subclass of progress_trace outputs to plain text.
  *
@@ -30,3 +34,8 @@ class text_progress_trace extends progress_trace {
         mtrace(str_repeat('  ', $depth) . $message);
     }
 }
+
+// Alias this class to the old name.
+// This file will be autoloaded by the legacyclasses autoload system.
+// In future all uses of this class will be corrected and the legacy references will be removed.
+class_alias(text_progress_trace::class, \text_progress_trace::class);