diff --git a/.gitattributes b/.gitattributes
index 84c7add05..14c3c3594 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,4 +1,3 @@
 /Tests export-ignore
 /phpunit.xml.dist export-ignore
-/.gitattributes export-ignore
-/.gitignore export-ignore
+/.git* export-ignore
diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
new file mode 100644
index 000000000..4689c4dad
--- /dev/null
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -0,0 +1,8 @@
+Please do not submit any Pull Requests here. They will be closed.
+---
+
+Please submit your PR here instead:
+https://github.com/symfony/symfony
+
+This repository is what we call a "subtree split": a read-only subset of that main repository.
+We're looking forward to your PR there!
diff --git a/.github/workflows/close-pull-request.yml b/.github/workflows/close-pull-request.yml
new file mode 100644
index 000000000..e55b47817
--- /dev/null
+++ b/.github/workflows/close-pull-request.yml
@@ -0,0 +1,20 @@
+name: Close Pull Request
+
+on:
+  pull_request_target:
+    types: [opened]
+
+jobs:
+  run:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: superbrothers/close-pull-request@v3
+      with:
+        comment: |
+          Thanks for your Pull Request! We love contributions.
+
+          However, you should instead open your PR on the main repository:
+          https://github.com/symfony/symfony
+
+          This repository is what we call a "subtree split": a read-only subset of that main repository.
+          We're looking forward to your PR there!
diff --git a/Tests/Session/Storage/Handler/AbstractRedisSessionHandlerTestCase.php b/Tests/Session/Storage/Handler/AbstractRedisSessionHandlerTestCase.php
index 4df1553c8..a582909a0 100644
--- a/Tests/Session/Storage/Handler/AbstractRedisSessionHandlerTestCase.php
+++ b/Tests/Session/Storage/Handler/AbstractRedisSessionHandlerTestCase.php
@@ -89,6 +89,7 @@ public function testUseSessionGcMaxLifetimeAsTimeToLive()
 
     public function testDestroySession()
     {
+        $this->storage->open('', 'test');
         $this->redisClient->set(self::PREFIX.'id', 'foo');
 
         $this->assertTrue((bool) $this->redisClient->exists(self::PREFIX.'id'));
diff --git a/Tests/Session/Storage/Handler/MemcachedSessionHandlerTest.php b/Tests/Session/Storage/Handler/MemcachedSessionHandlerTest.php
index 379fcb0d1..60bae22c3 100644
--- a/Tests/Session/Storage/Handler/MemcachedSessionHandlerTest.php
+++ b/Tests/Session/Storage/Handler/MemcachedSessionHandlerTest.php
@@ -109,6 +109,7 @@ public function testWriteSessionWithLargeTTL()
 
     public function testDestroySession()
     {
+        $this->storage->open('', 'sid');
         $this->memcached
             ->expects($this->once())
             ->method('delete')
diff --git a/Tests/Session/Storage/Handler/MigratingSessionHandlerTest.php b/Tests/Session/Storage/Handler/MigratingSessionHandlerTest.php
index eb988dfd6..959ffab97 100644
--- a/Tests/Session/Storage/Handler/MigratingSessionHandlerTest.php
+++ b/Tests/Session/Storage/Handler/MigratingSessionHandlerTest.php
@@ -52,6 +52,8 @@ public function testClose()
 
     public function testDestroy()
     {
+        $this->dualHandler->open('/path/to/save/location', 'xyz');
+
         $sessionId = 'xyz';
 
         $this->currentHandler->expects($this->once())
diff --git a/Tests/Session/Storage/Handler/MongoDbSessionHandlerTest.php b/Tests/Session/Storage/Handler/MongoDbSessionHandlerTest.php
index f43115a13..04dfdbef8 100644
--- a/Tests/Session/Storage/Handler/MongoDbSessionHandlerTest.php
+++ b/Tests/Session/Storage/Handler/MongoDbSessionHandlerTest.php
@@ -166,6 +166,8 @@ public function testDestroy()
         $this->storage->write('foo', 'bar');
         $this->storage->write('baz', 'qux');
 
+        $this->storage->open('test', 'test');
+
         $this->assertTrue($this->storage->destroy('foo'));
 
         $sessions = $this->getSessions();
diff --git a/Tests/Session/Storage/Handler/PdoSessionHandlerTest.php b/Tests/Session/Storage/Handler/PdoSessionHandlerTest.php
index ede4703aa..55a238732 100644
--- a/Tests/Session/Storage/Handler/PdoSessionHandlerTest.php
+++ b/Tests/Session/Storage/Handler/PdoSessionHandlerTest.php
@@ -224,6 +224,7 @@ public function testWrongUsageStillWorks()
     {
         // wrong method sequence that should no happen, but still works
         $storage = new PdoSessionHandler($this->getMemorySqlitePdo());
+        $storage->open('', 'sid');
         $storage->write('id', 'data');
         $storage->write('other_id', 'other_data');
         $storage->destroy('inexistent');
diff --git a/Tests/Session/Storage/Handler/StrictSessionHandlerTest.php b/Tests/Session/Storage/Handler/StrictSessionHandlerTest.php
index 68db5f4cf..27c952cd2 100644
--- a/Tests/Session/Storage/Handler/StrictSessionHandlerTest.php
+++ b/Tests/Session/Storage/Handler/StrictSessionHandlerTest.php
@@ -130,6 +130,7 @@ public function testWriteEmptyNewSession()
         $handler->expects($this->never())->method('write');
         $handler->expects($this->once())->method('destroy')->willReturn(true);
         $proxy = new StrictSessionHandler($handler);
+        $proxy->open('path', 'name');
 
         $this->assertFalse($proxy->validateId('id'));
         $this->assertSame('', $proxy->read('id'));
@@ -144,6 +145,7 @@ public function testWriteEmptyExistingSession()
         $handler->expects($this->never())->method('write');
         $handler->expects($this->once())->method('destroy')->willReturn(true);
         $proxy = new StrictSessionHandler($handler);
+        $proxy->open('path', 'name');
 
         $this->assertSame('data', $proxy->read('id'));
         $this->assertTrue($proxy->write('id', ''));
@@ -155,6 +157,7 @@ public function testDestroy()
         $handler->expects($this->once())->method('destroy')
             ->with('id')->willReturn(true);
         $proxy = new StrictSessionHandler($handler);
+        $proxy->open('path', 'name');
 
         $this->assertTrue($proxy->destroy('id'));
     }
@@ -166,6 +169,7 @@ public function testDestroyNewSession()
             ->with('id')->willReturn('');
         $handler->expects($this->once())->method('destroy')->willReturn(true);
         $proxy = new StrictSessionHandler($handler);
+        $proxy->open('path', 'name');
 
         $this->assertSame('', $proxy->read('id'));
         $this->assertTrue($proxy->destroy('id'));
@@ -181,6 +185,7 @@ public function testDestroyNonEmptyNewSession()
         $handler->expects($this->once())->method('destroy')
             ->with('id')->willReturn(true);
         $proxy = new StrictSessionHandler($handler);
+        $proxy->open('path', 'name');
 
         $this->assertSame('', $proxy->read('id'));
         $this->assertTrue($proxy->write('id', 'data'));