diff --git a/src/Composer/Console/Application.php b/src/Composer/Console/Application.php
index 9e585e614..01a2497b7 100644
--- a/src/Composer/Console/Application.php
+++ b/src/Composer/Console/Application.php
@@ -339,7 +339,8 @@ class Application extends BaseApplication
 
             // Check system temp folder for usability as it can cause weird runtime issues otherwise
             Silencer::call(static function () use ($io): void {
-                $tempfile = sys_get_temp_dir() . '/temp-' . getmypid() . '-' . md5(microtime());
+                $pid = function_exists('getmypid') ? getmypid() . '-' : '';
+                $tempfile = sys_get_temp_dir() . '/temp-' . $pid . md5(microtime());
                 if (!(file_put_contents($tempfile, __FILE__) && (file_get_contents($tempfile) === __FILE__) && unlink($tempfile) && !file_exists($tempfile))) {
                     $io->writeError(sprintf('<error>PHP temp directory (%s) does not exist or is not writable to Composer. Set sys_temp_dir in your php.ini</error>', sys_get_temp_dir()));
                 }
diff --git a/src/Composer/Installer/BinaryInstaller.php b/src/Composer/Installer/BinaryInstaller.php
index 827c8178c..ba50fe17f 100644
--- a/src/Composer/Installer/BinaryInstaller.php
+++ b/src/Composer/Installer/BinaryInstaller.php
@@ -337,8 +337,7 @@ if (PHP_VERSION_ID < 80000) {
         (function_exists('stream_get_wrappers') && in_array('phpvfscomposer', stream_get_wrappers(), true))
         || (function_exists('stream_wrapper_register') && stream_wrapper_register('phpvfscomposer', 'Composer\BinProxyWrapper'))
     ) {
-        include("phpvfscomposer://" . $binPathExported);
-        exit(0);
+        return include("phpvfscomposer://" . $binPathExported);
     }
 }
 
@@ -360,7 +359,7 @@ namespace Composer;
 
 $globalsCode
 $streamProxyCode
-include $binPathExported;
+return include $binPathExported;
 
 PROXY;
         }
diff --git a/src/Composer/Plugin/PluginManager.php b/src/Composer/Plugin/PluginManager.php
index 14eb40211..65c83c17b 100644
--- a/src/Composer/Plugin/PluginManager.php
+++ b/src/Composer/Plugin/PluginManager.php
@@ -264,7 +264,7 @@ class PluginManager
                 if ($separatorPos) {
                     $className = substr($class, $separatorPos + 1);
                 }
-                $code = Preg::replace('{^((?:final\s+)?(?:\s*))class\s+('.preg_quote($className).')}mi', '$1class $2_composer_tmp'.self::$classCounter, $code, 1);
+                $code = Preg::replace('{^((?:(?:final|readonly)\s+)*(?:\s*))class\s+('.preg_quote($className).')}mi', '$1class $2_composer_tmp'.self::$classCounter, $code, 1);
                 $code = strtr($code, [
                     '__FILE__' => var_export($path, true),
                     '__DIR__' => var_export(dirname($path), true),