diff --git a/src/TypeGenerator.php b/src/TypeGenerator.php
index 1220fa679..a330a1ae8 100644
--- a/src/TypeGenerator.php
+++ b/src/TypeGenerator.php
@@ -125,6 +125,16 @@ public function mapAnnotatedObject(string $annotatedObjectClassName): MutableInt
             $type->description = $resolvedDescription;
         }
 
+        // Instantiating the annotated object via the container (above) can reentrantly resolve and
+        // register this very type — e.g. a dependency in the container graph references it. If so,
+        // reuse that instance rather than return the duplicate we just built, which would later trip
+        // the registry identity check in RecursiveTypeMapper (the first-request crash in long-lived
+        // workers). mapFactoryMethod() guards its own cache the same way after its container->get.
+        // See https://github.com/thecodingmachine/graphqlite/issues/531
+        if ($this->typeRegistry->hasType($type->name)) {
+            return $this->typeRegistry->getMutableInterface($type->name);
+        }
+
         return $type;
     }
 
diff --git a/tests/TypeGeneratorTest.php b/tests/TypeGeneratorTest.php
index 131e4ec22..3a15de506 100644
--- a/tests/TypeGeneratorTest.php
+++ b/tests/TypeGeneratorTest.php
@@ -51,4 +51,36 @@ public function testextendAnnotatedObjectException(): void
         $this->expectException(MissingAnnotationException::class);
         $typeGenerator->extendAnnotatedObject(new stdClass(), $type);
     }
+
+    public function testMapAnnotatedObjectReusesTypeRegisteredReentrantlyDuringContainerGet(): void
+    {
+        // Reproduces the cold-registry race behind #531: instantiating the annotated object via the
+        // container reentrantly resolves (and registers) this same type. mapAnnotatedObject must
+        // reuse that instance rather than build a duplicate — otherwise RecursiveTypeMapper's
+        // identity check throws "Cached type in registry is not the type returned by type mapper."
+        // on the first request in long-lived workers (Swoole/RoadRunner/FrankenPHP).
+        $typeRegistry = $this->getTypeRegistry();
+        $reentrantlyRegistered = new MutableObjectType(['name' => 'TestObject', 'fields' => []], TypeFoo::class);
+
+        $container = new LazyContainer([
+            TypeFoo::class => static function () use ($typeRegistry, $reentrantlyRegistered) {
+                if (! $typeRegistry->hasType('TestObject')) {
+                    $typeRegistry->registerType($reentrantlyRegistered);
+                }
+
+                return new TypeFoo();
+            },
+        ]);
+
+        $typeGenerator = new TypeGenerator(
+            $this->getAnnotationReader(),
+            new NamingStrategy(),
+            $typeRegistry,
+            $container,
+            $this->getTypeMapper(),
+            $this->getFieldsBuilder(),
+        );
+
+        $this->assertSame($reentrantlyRegistered, $typeGenerator->mapAnnotatedObject(TypeFoo::class));
+    }
 }