diff --git a/src/Symfony/Bridge/Doctrine/DependencyInjection/AbstractDoctrineExtension.php b/src/Symfony/Bridge/Doctrine/DependencyInjection/AbstractDoctrineExtension.php
index b9cac9f71845a..37875b53b570a 100644
--- a/src/Symfony/Bridge/Doctrine/DependencyInjection/AbstractDoctrineExtension.php
+++ b/src/Symfony/Bridge/Doctrine/DependencyInjection/AbstractDoctrineExtension.php
@@ -16,7 +16,6 @@
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Definition;
 use Symfony\Component\DependencyInjection\Reference;
-use Symfony\Component\Config\Resource\FileResource;
 
 /**
  * This abstract classes groups common code that Doctrine Object Manager extensions (ORM, MongoDB, CouchDB) need.
@@ -268,30 +267,28 @@ protected function assertValidMappingConfiguration(array $mappingConfig, $object
      */
     protected function detectMetadataDriver($dir, ContainerBuilder $container)
     {
-        // add the closest existing directory as a resource
         $configPath = $this->getMappingResourceConfigDirectory();
-        $resource = $dir.'/'.$configPath;
-        while (!is_dir($resource)) {
-            $resource = dirname($resource);
-        }
-
-        $container->addResource(new FileResource($resource));
-
         $extension = $this->getMappingResourceExtension();
-        if (($files = glob($dir.'/'.$configPath.'/*.'.$extension.'.xml')) && count($files)) {
-            return 'xml';
-        } elseif (($files = glob($dir.'/'.$configPath.'/*.'.$extension.'.yml')) && count($files)) {
-            return 'yml';
-        } elseif (($files = glob($dir.'/'.$configPath.'/*.'.$extension.'.php')) && count($files)) {
-            return 'php';
-        }
 
-        // add the directory itself as a resource
-        $container->addResource(new FileResource($dir));
+        if (glob($dir.'/'.$configPath.'/*.'.$extension.'.xml')) {
+            $driver = 'xml';
+        } elseif (glob($dir.'/'.$configPath.'/*.'.$extension.'.yml')) {
+            $driver = 'yml';
+        } elseif (glob($dir.'/'.$configPath.'/*.'.$extension.'.php')) {
+            $driver = 'php';
+        } else {
+            // add the closest existing directory as a resource
+            $resource = $dir.'/'.$configPath;
+            while (!is_dir($resource)) {
+                $resource = dirname($resource);
+            }
+            $container->fileExists($resource, false);
 
-        if (is_dir($dir.'/'.$this->getMappingObjectDefaultName())) {
-            return 'annotation';
+            return $container->fileExists($dir.'/'.$this->getMappingObjectDefaultName(), false) ? 'annotation' : null;
         }
+        $container->fileExists($dir.'/'.$configPath, false);
+
+        return $driver;
     }
 
     /**
diff --git a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
index 88ac0c0655e9d..0203f114bc699 100644
--- a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
+++ b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
@@ -23,7 +23,6 @@
 use Symfony\Component\DependencyInjection\Exception\LogicException;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\Loader\XmlFileLoader;
-use Symfony\Component\Config\Resource\FileResource;
 use Symfony\Component\Finder\Finder;
 use Symfony\Component\HttpKernel\DependencyInjection\Extension;
 use Symfony\Component\Config\FileLocator;
@@ -994,8 +993,7 @@ private function getValidatorMappingFiles(ContainerBuilder $container, array &$f
     {
         if (interface_exists('Symfony\Component\Form\FormInterface')) {
             $reflClass = new \ReflectionClass('Symfony\Component\Form\FormInterface');
-            $files['xml'][] = $file = dirname($reflClass->getFileName()).'/Resources/config/validation.xml';
-            $container->addResource(new FileResource($file));
+            $files['xml'][] = dirname($reflClass->getFileName()).'/Resources/config/validation.xml';
         }
 
         foreach ($container->getParameter('kernel.bundles_metadata') as $bundle) {
diff --git a/src/Symfony/Component/Config/Resource/ComposerResource.php b/src/Symfony/Component/Config/Resource/ComposerResource.php
new file mode 100644
index 0000000000000..56224d16c01d8
--- /dev/null
+++ b/src/Symfony/Component/Config/Resource/ComposerResource.php
@@ -0,0 +1,94 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Config\Resource;
+
+/**
+ * ComposerResource tracks the PHP version and Composer dependencies.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
+ */
+class ComposerResource implements SelfCheckingResourceInterface, \Serializable
+{
+    private $versions;
+    private $vendors;
+
+    private static $runtimeVersion;
+    private static $runtimeVendors;
+
+    public function __construct()
+    {
+        self::refresh();
+        $this->versions = self::$runtimeVersion;
+        $this->vendors = self::$runtimeVendors;
+    }
+
+    public function getVendors()
+    {
+        return array_keys($this->vendors);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function __toString()
+    {
+        return __CLASS__;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isFresh($timestamp)
+    {
+        self::refresh();
+
+        if (self::$runtimeVersion !== $this->versions) {
+            return false;
+        }
+
+        return self::$runtimeVendors === $this->vendors;
+    }
+
+    public function serialize()
+    {
+        return serialize(array($this->versions, $this->vendors));
+    }
+
+    public function unserialize($serialized)
+    {
+        list($this->versions, $this->vendors) = unserialize($serialized);
+    }
+
+    private static function refresh()
+    {
+        if (null !== self::$runtimeVersion) {
+            return;
+        }
+
+        self::$runtimeVersion = array();
+        self::$runtimeVendors = array();
+
+        foreach (get_loaded_extensions() as $ext) {
+            self::$runtimeVersion[$ext] = phpversion($ext);
+        }
+
+        foreach (get_declared_classes() as $class) {
+            if ('C' === $class[0] && 0 === strpos($class, 'ComposerAutoloaderInit')) {
+                $r = new \ReflectionClass($class);
+                $v = dirname(dirname($r->getFileName()));
+                if (file_exists($v.'/composer/installed.json')) {
+                    self::$runtimeVendors[$v] = @filemtime($v.'/composer/installed.json');
+                }
+            }
+        }
+    }
+}
diff --git a/src/Symfony/Component/Config/Resource/ReflectionClassResource.php b/src/Symfony/Component/Config/Resource/ReflectionClassResource.php
index 23aef37c0c182..a8e1f9611b99a 100644
--- a/src/Symfony/Component/Config/Resource/ReflectionClassResource.php
+++ b/src/Symfony/Component/Config/Resource/ReflectionClassResource.php
@@ -19,12 +19,14 @@ class ReflectionClassResource implements SelfCheckingResourceInterface, \Seriali
     private $files = array();
     private $className;
     private $classReflector;
+    private $excludedVendors = array();
     private $hash;
 
-    public function __construct(\ReflectionClass $classReflector)
+    public function __construct(\ReflectionClass $classReflector, $excludedVendors = array())
     {
         $this->className = $classReflector->name;
         $this->classReflector = $classReflector;
+        $this->excludedVendors = $excludedVendors;
     }
 
     public function isFresh($timestamp)
@@ -75,7 +77,15 @@ private function loadFiles(\ReflectionClass $class)
         do {
             $file = $class->getFileName();
             if (false !== $file && file_exists($file)) {
-                $this->files[$file] = null;
+                foreach ($this->excludedVendors as $vendor) {
+                    if (0 === strpos($file, $vendor) && false !== strpbrk(substr($file, strlen($vendor), 1), '/'.DIRECTORY_SEPARATOR)) {
+                        $file = false;
+                        break;
+                    }
+                }
+                if ($file) {
+                    $this->files[$file] = null;
+                }
             }
             foreach ($class->getTraits() as $v) {
                 $this->loadFiles($v);
diff --git a/src/Symfony/Component/Config/Tests/Resource/ComposerResourceTest.php b/src/Symfony/Component/Config/Tests/Resource/ComposerResourceTest.php
new file mode 100644
index 0000000000000..e617f178023c7
--- /dev/null
+++ b/src/Symfony/Component/Config/Tests/Resource/ComposerResourceTest.php
@@ -0,0 +1,46 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Config\Tests\Resource;
+
+use Composer\Autoload\ClassLoader;
+use Symfony\Component\Config\Resource\ComposerResource;
+
+class ComposerResourceTest extends \PHPUnit_Framework_TestCase
+{
+    public function testGetVendor()
+    {
+        $res = new ComposerResource();
+
+        $r = new \ReflectionClass(ClassLoader::class);
+        $found = false;
+
+        foreach ($res->getVendors() as $vendor) {
+            if ($vendor && 0 === strpos($r->getFileName(), $vendor)) {
+                $found = true;
+                break;
+            }
+        }
+
+        $this->assertTrue($found);
+    }
+
+    public function testSerializeUnserialize()
+    {
+        $res = new ComposerResource();
+        $ser = unserialize(serialize($res));
+
+        $this->assertTrue($res->isFresh(0));
+        $this->assertTrue($ser->isFresh(0));
+
+        $this->assertEquals($res, $ser);
+    }
+}
diff --git a/src/Symfony/Component/DependencyInjection/Compiler/FactoryReturnTypePass.php b/src/Symfony/Component/DependencyInjection/Compiler/FactoryReturnTypePass.php
index eaeead071796f..3ba4a8caa02f2 100644
--- a/src/Symfony/Component/DependencyInjection/Compiler/FactoryReturnTypePass.php
+++ b/src/Symfony/Component/DependencyInjection/Compiler/FactoryReturnTypePass.php
@@ -11,7 +11,6 @@
 
 namespace Symfony\Component\DependencyInjection\Compiler;
 
-use Symfony\Component\Config\Resource\FileResource;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Definition;
 use Symfony\Component\DependencyInjection\Reference;
@@ -67,7 +66,7 @@ private function updateDefinition(ContainerBuilder $container, $id, Definition $
             try {
                 $m = new \ReflectionFunction($factory);
                 if (false !== $m->getFileName() && file_exists($m->getFileName())) {
-                    $container->addResource(new FileResource($m->getFileName()));
+                    $container->fileExists($m->getFileName());
                 }
             } catch (\ReflectionException $e) {
                 return;
diff --git a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
index d68688c6029c1..5aa32b975ee8b 100644
--- a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
+++ b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
@@ -26,6 +26,7 @@
 use Symfony\Component\DependencyInjection\Extension\ExtensionInterface;
 use Symfony\Component\DependencyInjection\ParameterBag\EnvPlaceholderParameterBag;
 use Symfony\Component\Config\Resource\ClassExistenceResource;
+use Symfony\Component\Config\Resource\ComposerResource;
 use Symfony\Component\Config\Resource\DirectoryResource;
 use Symfony\Component\Config\Resource\FileExistenceResource;
 use Symfony\Component\Config\Resource\FileResource;
@@ -108,6 +109,11 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
      */
     private $envCounters = array();
 
+    /**
+     * @var string[] the list of vendor directories
+     */
+    private $vendors;
+
     /**
      * Sets the track resources flag.
      *
@@ -269,13 +275,13 @@ public function addObjectResource($object)
                 }
                 $file = $interface->getFileName();
                 if (false !== $file && file_exists($file)) {
-                    $this->addResource(new FileResource($file));
+                    $this->fileExists($file);
                 }
             }
             do {
                 $file = $class->getFileName();
                 if (false !== $file && file_exists($file)) {
-                    $this->addResource(new FileResource($file));
+                    $this->fileExists($file);
                 }
                 foreach ($class->getTraitNames() as $name) {
                     $this->addObjectResource($name);
@@ -337,7 +343,11 @@ public function getReflectionClass($class, $koWithThrowingAutoloader = false)
             if (!$classReflector) {
                 $this->addResource($resource ?: new ClassExistenceResource($class, ClassExistenceResource::EXISTS_KO));
             } elseif (!$classReflector->isInternal()) {
-                $this->addResource(new ReflectionClassResource($classReflector));
+                $path = $classReflector->getFileName();
+
+                if (!$this->inVendors($path)) {
+                    $this->addResource(new ReflectionClassResource($classReflector, $this->vendors));
+                }
             }
             $this->classReflectors[$class] = $classReflector;
         }
@@ -360,7 +370,7 @@ public function fileExists($path, $trackContents = true)
     {
         $exists = file_exists($path);
 
-        if (!$this->trackResources) {
+        if (!$this->trackResources || $this->inVendors($path)) {
             return $exists;
         }
 
@@ -370,12 +380,10 @@ public function fileExists($path, $trackContents = true)
             return $exists;
         }
 
-        if ($trackContents) {
-            if (is_file($path)) {
-                $this->addResource(new FileResource($path));
-            } else {
-                $this->addResource(new DirectoryResource($path, is_string($trackContents) ? $trackContents : null));
-            }
+        if ($trackContents && is_dir($path)) {
+            $this->addResource(new DirectoryResource($path, is_string($trackContents) ? $trackContents : null));
+        } elseif ($trackContents || is_dir($path)) {
+            $this->addResource(new FileResource($path));
         }
 
         return $exists;
@@ -1488,4 +1496,22 @@ private function getExpressionLanguage()
 
         return $this->expressionLanguage;
     }
+
+    private function inVendors($path)
+    {
+        if (null === $this->vendors) {
+            $resource = new ComposerResource();
+            $this->vendors = $resource->getVendors();
+            $this->addResource($resource);
+        }
+        $path = realpath($path) ?: $path;
+
+        foreach ($this->vendors as $vendor) {
+            if (0 === strpos($path, $vendor) && false !== strpbrk(substr($path, strlen($vendor), 1), '/'.DIRECTORY_SEPARATOR)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
 }
diff --git a/src/Symfony/Component/DependencyInjection/Loader/DirectoryLoader.php b/src/Symfony/Component/DependencyInjection/Loader/DirectoryLoader.php
index ffb8853011134..3ab4c5dc82e7e 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/DirectoryLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/DirectoryLoader.php
@@ -27,7 +27,7 @@ public function load($file, $type = null)
     {
         $file = rtrim($file, '/');
         $path = $this->locator->locate($file);
-        $this->container->addResource(new DirectoryResource($path));
+        $this->container->fileExists($path, false);
 
         foreach (scandir($path) as $dir) {
             if ('.' !== $dir[0]) {
diff --git a/src/Symfony/Component/DependencyInjection/Loader/IniFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/IniFileLoader.php
index 224524e50e8b6..170e726396a5e 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/IniFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/IniFileLoader.php
@@ -29,7 +29,7 @@ public function load($resource, $type = null)
     {
         $path = $this->locator->locate($resource);
 
-        $this->container->addResource(new FileResource($path));
+        $this->container->fileExists($path);
 
         // first pass to catch parsing errors
         $result = parse_ini_file($path, true);
diff --git a/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php
index 5275ab5010f94..36ef0d4752bc9 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php
@@ -34,7 +34,7 @@ public function load($resource, $type = null)
 
         $path = $this->locator->locate($resource);
         $this->setCurrentDir(dirname($path));
-        $this->container->addResource(new FileResource($path));
+        $this->container->fileExists($path);
 
         include $path;
     }
diff --git a/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
index 4e1ee6ac12594..253cddd17f628 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
@@ -42,7 +42,7 @@ public function load($resource, $type = null)
 
         $xml = $this->parseFileToDOM($path);
 
-        $this->container->addResource(new FileResource($path));
+        $this->container->fileExists($path);
 
         // anonymous services
         $this->processAnonymousServices($xml, $path);
diff --git a/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
index ba29ca60b50df..861fba2be519b 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
@@ -72,7 +72,7 @@ public function load($resource, $type = null)
 
         $content = $this->loadFile($path);
 
-        $this->container->addResource(new FileResource($path));
+        $this->container->fileExists($path);
 
         // empty file
         if (null === $content) {
diff --git a/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php b/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
index 41a5702549a35..094d931a88901 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/ContainerBuilderTest.php
@@ -14,6 +14,7 @@
 require_once __DIR__.'/Fixtures/includes/classes.php';
 require_once __DIR__.'/Fixtures/includes/ProjectExtension.php';
 
+use Symfony\Component\Config\Resource\ComposerResource;
 use Symfony\Component\Config\Resource\ResourceInterface;
 use Symfony\Component\Config\Resource\DirectoryResource;
 use Symfony\Component\DependencyInjection\Alias;
@@ -614,7 +615,7 @@ public function testAddObjectResource()
 
         $resources = $container->getResources();
 
-        $this->assertCount(1, $resources, '1 resource was registered');
+        $this->assertCount(2, $resources, '2 resources were registered');
 
         /* @var $resource \Symfony\Component\Config\Resource\FileResource */
         $resource = end($resources);
@@ -640,7 +641,7 @@ public function testAddClassResource()
 
         $resources = $container->getResources();
 
-        $this->assertCount(1, $resources, '1 resource was registered');
+        $this->assertCount(2, $resources, '2 resources were registered');
 
         /* @var $resource \Symfony\Component\Config\Resource\FileResource */
         $resource = end($resources);
@@ -669,9 +670,9 @@ public function testGetReflectionClass()
 
         $resources = $container->getResources();
 
-        $this->assertCount(2, $resources, '2 resources were registered');
+        $this->assertCount(3, $resources, '3 resources were registered');
 
-        $this->assertSame('reflection.BarClass', (string) $resources[0]);
+        $this->assertSame('reflection.BarClass', (string) $resources[1]);
         $this->assertSame('BarMissingClass', (string) end($resources));
     }
 
@@ -715,6 +716,7 @@ public function testResources()
     public function testFileExists()
     {
         $container = new ContainerBuilder();
+        $A = new ComposerResource();
         $a = new FileResource(__DIR__.'/Fixtures/xml/services1.xml');
         $b = new FileResource(__DIR__.'/Fixtures/xml/services2.xml');
         $c = new DirectoryResource($dir = dirname($b));
@@ -728,7 +730,7 @@ public function testFileExists()
             }
         }
 
-        $this->assertEquals(array($a, $b, $c), $resources, '->getResources() returns an array of resources read for the current configuration');
+        $this->assertEquals(array($A, $a, $b, $c), $resources, '->getResources() returns an array of resources read for the current configuration');
     }
 
     public function testExtension()