diff --git a/CHANGELOG b/CHANGELOG
index 66db8fff221..71eb108199b 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,6 @@
 # 3.19.0 (2025-XX-XX)
 
- * n/a
+ * Add `LastModifiedExtensionInterface` and implementation in `AbstractExtension` to track modification of runtime classes
 
 # 3.18.0 (2024-12-29)
 
diff --git a/doc/advanced.rst b/doc/advanced.rst
index e07764b8770..bc7e5d376f4 100644
--- a/doc/advanced.rst
+++ b/doc/advanced.rst
@@ -868,7 +868,7 @@ must be autoload-able)::
             // implement the logic to create an instance of $class
             // and inject its dependencies
             // most of the time, it means using your dependency injection container
-            if ('CustomRuntimeExtension' === $class) {
+            if ('CustomTwigRuntime' === $class) {
                 return new $class(new Rot13Provider());
             } else {
                 // ...
@@ -884,9 +884,9 @@ must be autoload-able)::
     (``\Twig\RuntimeLoader\ContainerRuntimeLoader``).
 
 It is now possible to move the runtime logic to a new
-``CustomRuntimeExtension`` class and use it directly in the extension::
+``CustomTwigRuntime`` class and use it directly in the extension::
 
-    class CustomRuntimeExtension
+    class CustomTwigRuntime
     {
         private $rot13Provider;
 
@@ -906,13 +906,21 @@ It is now possible to move the runtime logic to a new
         public function getFunctions()
         {
             return [
-                new \Twig\TwigFunction('rot13', ['CustomRuntimeExtension', 'rot13']),
+                new \Twig\TwigFunction('rot13', ['CustomTwigRuntime', 'rot13']),
                 // or
-                new \Twig\TwigFunction('rot13', 'CustomRuntimeExtension::rot13'),
+                new \Twig\TwigFunction('rot13', 'CustomTwigRuntime::rot13'),
             ];
         }
     }
 
+.. note::
+
+    The extension class should implement the ``Twig\Extension\LastModifiedExtensionInterface``
+    interface to invalidate the template cache when the runtime class is modified.
+    The ``AbstractExtension`` class implements this interface and tracks the
+    runtime class if its name is the same as the extension class but ends with
+    ``Runtime`` instead of ``Extension``.
+
 Testing an Extension
 --------------------
 
diff --git a/src/Extension/AbstractExtension.php b/src/Extension/AbstractExtension.php
index a1b083b6884..4234df087f6 100644
--- a/src/Extension/AbstractExtension.php
+++ b/src/Extension/AbstractExtension.php
@@ -11,7 +11,7 @@
 
 namespace Twig\Extension;
 
-abstract class AbstractExtension implements ExtensionInterface
+abstract class AbstractExtension implements LastModifiedExtensionInterface
 {
     public function getTokenParsers()
     {
@@ -42,4 +42,21 @@ public function getOperators()
     {
         return [[], []];
     }
+
+    public function getLastModified(): int
+    {
+        $filename = (new \ReflectionClass($this))->getFileName();
+        if (!is_file($filename)) {
+            return 0;
+        }
+
+        $lastModified = filemtime($filename);
+
+        // Track modifications of the runtime class if it exists and follows the naming convention
+        if (str_ends_with($filename, 'Extension.php') && is_file($filename = substr($filename, 0, -13) . 'Runtime.php')) {
+            $lastModified = max($lastModified, filemtime($filename));
+        }
+
+        return $lastModified;
+    }
 }
diff --git a/src/Extension/EscaperExtension.php b/src/Extension/EscaperExtension.php
index 52531c436b5..9a05e4c7c65 100644
--- a/src/Extension/EscaperExtension.php
+++ b/src/Extension/EscaperExtension.php
@@ -57,6 +57,14 @@ public function getFilters(): array
         ];
     }
 
+    public function getLastModified(): int
+    {
+        return max(
+            parent::getLastModified(),
+            filemtime((new \ReflectionClass(EscaperRuntime::class))->getFileName()),
+        );
+    }
+
     /**
      * @deprecated since Twig 3.10
      */
diff --git a/src/Extension/LastModifiedExtensionInterface.php b/src/Extension/LastModifiedExtensionInterface.php
new file mode 100644
index 00000000000..4bab0c07cd3
--- /dev/null
+++ b/src/Extension/LastModifiedExtensionInterface.php
@@ -0,0 +1,23 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Twig\Extension;
+
+interface LastModifiedExtensionInterface extends ExtensionInterface
+{
+    /**
+     * Returns the last modification time of the extension for cache invalidation.
+     *
+     * This timestamp should be the last time the source code of the extension class
+     * and all its dependencies were modified (including the Runtime class).
+     */
+    public function getLastModified(): int;
+}
diff --git a/src/ExtensionSet.php b/src/ExtensionSet.php
index e8b3174cff4..18979228a7d 100644
--- a/src/ExtensionSet.php
+++ b/src/ExtensionSet.php
@@ -14,6 +14,7 @@
 use Twig\Error\RuntimeError;
 use Twig\Extension\ExtensionInterface;
 use Twig\Extension\GlobalsInterface;
+use Twig\Extension\LastModifiedExtensionInterface;
 use Twig\Extension\StagingExtension;
 use Twig\Node\Expression\Binary\AbstractBinary;
 use Twig\Node\Expression\Unary\AbstractUnary;
@@ -116,14 +117,19 @@ public function getLastModified(): int
             return $this->lastModified;
         }
 
+        $lastModified = 0;
         foreach ($this->extensions as $extension) {
-            $r = new \ReflectionObject($extension);
-            if (is_file($r->getFileName()) && ($extensionTime = filemtime($r->getFileName())) > $this->lastModified) {
-                $this->lastModified = $extensionTime;
+            if ($extension instanceof LastModifiedExtensionInterface) {
+                $lastModified = max($extension->getLastModified(), $lastModified);
+            } else {
+                $r = new \ReflectionObject($extension);
+                if (is_file($r->getFileName())) {
+                    $lastModified = max(filemtime($r->getFileName()), $lastModified);
+                }
             }
         }
 
-        return $this->lastModified;
+        return $this->lastModified = $lastModified;
     }
 
     public function addExtension(ExtensionInterface $extension): void
diff --git a/tests/Extension/CoreTest.php b/tests/Extension/CoreTest.php
index 6bb74807f86..edce0d3eede 100644
--- a/tests/Extension/CoreTest.php
+++ b/tests/Extension/CoreTest.php
@@ -393,6 +393,11 @@ public function testSandboxedIncludeWithPreloadedTemplate()
         $this->expectException(SecurityError::class);
         $twig->render('index');
     }
+
+    public function testLastModified()
+    {
+        $this->assertGreaterThan(1000000000, (new CoreExtension())->getLastModified());
+    }
 }
 
 final class CoreTestIteratorAggregate implements \IteratorAggregate
diff --git a/tests/Extension/EscaperTest.php b/tests/Extension/EscaperTest.php
index 436d1790f52..28df82db570 100644
--- a/tests/Extension/EscaperTest.php
+++ b/tests/Extension/EscaperTest.php
@@ -70,6 +70,11 @@ public function testCustomEscapersOnMultipleEnvs()
         $this->assertSame('foo**ISO-8859-1**UTF-8', $env1->getRuntime(EscaperRuntime::class)->escape('foo', 'foo', 'ISO-8859-1'));
         $this->assertSame('foo**ISO-8859-1**UTF-8**again', $env2->getRuntime(EscaperRuntime::class)->escape('foo', 'foo', 'ISO-8859-1'));
     }
+
+    public function testLastModified()
+    {
+        $this->assertGreaterThan(1000000000, (new EscaperExtension())->getLastModified());
+    }
 }
 
 function legacy_escaper(Environment $twig, $string, $charset)