diff --git a/src/Api/Server.php b/src/Api/Server.php
index 1769512..31d441b 100644
--- a/src/Api/Server.php
+++ b/src/Api/Server.php
@@ -5,8 +5,8 @@
 namespace Ecodev\Felix\Api;
 
 use Doctrine\DBAL\Exception\DriverException;
-use GraphQL\Error\ClientAware;
 use GraphQL\Error\DebugFlag;
+use GraphQL\Error\UserError;
 use GraphQL\Executor\ExecutionResult;
 use GraphQL\GraphQL;
 use GraphQL\Server\ServerConfig;
@@ -102,9 +102,16 @@ private function handleError(Throwable $exception, callable $formatter): array
 
         $result = $formatter($exception);
 
-        if (!$exception instanceof ClientAware || !$exception->isClientSafe()) {
-            $result['extensions'] ??= [];
-            $result['extensions']['category'] = 'internal';
+        // Invalid variable that end-user might have crafted via the URL
+        $isInvalidVariables = preg_match('~^Variable \".*\" got invalid value ~', $exception->getMessage());
+        $isFelixException = $exception->getPrevious() instanceof Exception;
+        if ($isFelixException || $isInvalidVariables) {
+            $result['extensions']['showSnack'] = true;
+        }
+
+        // Not found object
+        if ($exception->getPrevious() instanceof UserError && preg_match('~^Entity not found for class `~', $exception->getMessage())) {
+            $result['extensions']['objectNotFound'] = true;
         }
 
         return $result;
diff --git a/tests/Api/ServerTest.php b/tests/Api/ServerTest.php
index c84f15a..29dcdab 100644
--- a/tests/Api/ServerTest.php
+++ b/tests/Api/ServerTest.php
@@ -5,21 +5,81 @@
 namespace EcodevTests\Felix\Api;
 
 use Ecodev\Felix\Api\Server;
+use EcodevTests\Felix\Traits\TestWithContainer;
+use Exception;
+use GraphQL\Error\UserError;
 use GraphQL\Executor\ExecutionResult;
 use GraphQL\Type\Definition\ObjectType;
+use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Schema;
+use Laminas\ConfigAggregator\ArrayProvider;
+use Laminas\ConfigAggregator\ConfigAggregator;
 use Laminas\Diactoros\CallbackStream;
 use Laminas\Diactoros\ServerRequest;
+use Laminas\Log\LoggerInterface;
 use PHPUnit\Framework\TestCase;
 
 class ServerTest extends TestCase
 {
+    use TestWithContainer;
+
+    /**
+     * @var LoggerInterface&\PHPUnit\Framework\MockObject\MockObject
+     */
+    private LoggerInterface $logger;
+
+    protected function setUp(): void
+    {
+        $this->logger = $this->createMock(LoggerInterface::class);
+        $aggregator = new ConfigAggregator([
+            new ArrayProvider([
+                'dependencies' => [
+                    'factories' => [
+                        LoggerInterface::class => fn () => $this->logger,
+                    ],
+                ],
+            ]),
+        ]);
+
+        $this->createContainer($aggregator);
+    }
+
     /**
      * @dataProvider providerExecute
      */
-    public function testExecute(string $body, array $expected): void
+    public function testExecute(string $body, array $expected, string $expectedLog = ''): void
     {
-        $schema = new Schema(['query' => new ObjectType(['name' => 'Query', 'fields' => []])]);
+        $schema = new Schema(['query' => new ObjectType([
+            'name' => 'Query',
+            'fields' => [
+                'nativeException' => [
+                    'type' => Type::boolean(),
+                    'resolve' => fn () => throw new Exception('Fake message'),
+                ],
+                'felixException' => [
+                    'type' => Type::boolean(),
+                    'resolve' => fn () => throw new \Ecodev\Felix\Api\Exception('Fake message'),
+                ],
+                'notFoundException' => [
+                    'type' => Type::boolean(),
+                    'resolve' => fn () => throw new UserError('Entity not found for class `foo` and ID `bar`.'),
+                ],
+                'invalidVariables' => [
+                    'args' => [
+                        'myArg' => Type::boolean(),
+                    ],
+                    'type' => Type::boolean(),
+                    'resolve' => fn () => true,
+                ],
+            ],
+        ])]);
+
+        if ($expectedLog) {
+            $this->logger->expects(self::once())->method('err')->with($expectedLog);
+        } else {
+            $this->logger->expects(self::never())->method('err');
+        }
+
         $server = new Server($schema, false);
         $request = new ServerRequest(method: 'POST', body: new CallbackStream(fn () => $body));
         $request = $request->withHeader('content-type', 'application/json');
@@ -73,5 +133,132 @@ public static function providerExecute(): iterable
                 ],
             ],
         ];
+
+        yield 'native exception' => [
+            '{"query": "{ nativeException }"}',
+            [
+                'errors' => [
+                    [
+                        'message' => 'Internal server error',
+                        'locations' => [
+                            [
+                                'line' => 1,
+                                'column' => 3,
+                            ],
+                        ],
+                        'path' => [
+                            'nativeException',
+                        ],
+                    ],
+                ],
+                'data' => [
+                    'nativeException' => null,
+                ],
+            ],
+            <<<STRING
+                Fake message
+
+                GraphQL request (1:3)
+                1: { nativeException }
+                     ^
+
+                STRING
+        ];
+
+        yield 'Felix exception shows snackbar' => [
+            '{"query": "{ felixException }"}',
+            [
+                'errors' => [
+                    [
+                        'message' => 'Fake message',
+                        'locations' => [
+                            [
+                                'line' => 1,
+                                'column' => 3,
+                            ],
+                        ],
+                        'path' => [
+                            'felixException',
+                        ],
+                        'extensions' => [
+                            'showSnack' => true,
+                        ],
+                    ],
+                ],
+                'data' => [
+                    'felixException' => null,
+                ],
+            ],
+            <<<STRING
+                Fake message
+
+                GraphQL request (1:3)
+                1: { felixException }
+                     ^
+
+                STRING
+        ];
+
+        yield 'not found exception does not show snackbar but is flagged' => [
+            '{"query": "{ notFoundException }"}',
+            [
+                'errors' => [
+                    [
+                        'message' => 'Entity not found for class `foo` and ID `bar`.',
+                        'locations' => [
+                            [
+                                'line' => 1,
+                                'column' => 3,
+                            ],
+                        ],
+                        'path' => [
+                            'notFoundException',
+                        ],
+                        'extensions' => [
+                            'objectNotFound' => true,
+                        ],
+                    ],
+                ],
+                'data' => [
+                    'notFoundException' => null,
+                ],
+            ],
+            <<<STRING
+                Entity not found for class `foo` and ID `bar`.
+
+                GraphQL request (1:3)
+                1: { notFoundException }
+                     ^
+
+                STRING
+        ];
+
+        yield 'invalidVariables shows snackbar' => [
+            '{"query": "query ($v: Boolean) { invalidVariables(myArg: $v) }", "variables": {"v": 123}}',
+            [
+                'errors' => [
+                    [
+                        'message' => 'Variable "$v" got invalid value 123; Boolean cannot represent a non boolean value: 123',
+                        'locations' => [
+                            [
+                                'line' => 1,
+                                'column' => 8,
+                            ],
+                        ],
+                        'extensions' => [
+                            'showSnack' => true,
+                        ],
+                    ],
+                ],
+            ],
+            <<<STRING
+                Variable "\$v" got invalid value 123; Boolean cannot represent a non boolean value: 123
+
+                GraphQL request (1:8)
+                1: query (\$v: Boolean) { invalidVariables(myArg: \$v) }
+                          ^
+
+                STRING
+        ];
     }
 }