diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 096380d0c7f..e24473440de 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -306,7 +306,7 @@ jobs:
         continue-on-error: true
 
   phpunit-components:
-    name: PHPUnit ${{ matrix.component }} (PHP ${{ matrix.php.version }} ${{ matrix.php.coverage && 'coverage' || '' }}${{ matrix.php.lowest && 'lowest' || '' }}${{ matrix.php.minimal-changes && 'minimal-changes' || '' }})
+    name: PHPUnit ${{ matrix.component }} (PHP ${{ matrix.php.version }} ${{ matrix.php.coverage && 'coverage' || '' }}${{ matrix.php.lowest && 'lowest' || '' }}${{ matrix.php.minimal-changes && 'minimal-changes' || '' }}${{ matrix.opensearch && 'opensearch' || '' }})
     runs-on: ubuntu-latest
     timeout-minutes: 20
     strategy:
@@ -338,6 +338,11 @@ jobs:
           - api-platform/state
           - api-platform/symfony
           - api-platform/validator
+        include:
+          - php:
+              version: '8.5'
+            component: api-platform/elasticsearch
+            opensearch: true
       fail-fast: false
     steps:
       - name: Checkout
@@ -368,6 +373,11 @@ jobs:
         run: |
           cd $(composer ${{matrix.component}} --cwd)
           composer update${{ matrix.php.lowest && ' --prefer-lowest --prefer-source' || '' }}${{ matrix.php.minimal-changes && ' --minimal-changes' || '' }}
+      - name: Install OpenSearch PHP client
+        if: ${{ matrix.opensearch }}
+        run: |
+          cd $(composer ${{matrix.component}} --cwd)
+          composer require --dev opensearch-project/opensearch-php "^2.5" -W
       - name: Run ${{ matrix.component }} tests
         run: |
           mkdir -p /tmp/build/logs/phpunit
@@ -888,6 +898,64 @@ jobs:
       - name: Run Behat tests
         run: vendor/bin/behat --out=std --format=progress --profile=elasticsearch --no-interaction
 
+  opensearch:
+    name: Behat (PHP ${{ matrix.php }}) (OpenSearch ${{ matrix.opensearch-version }})
+    runs-on: ubuntu-22.04
+    timeout-minutes: 20
+    strategy:
+      matrix:
+        include:
+          - php: '8.5'
+            opensearch-version: '2.19.4'
+            extensions: 'intl, bcmath, curl, openssl, mbstring'
+      fail-fast: false
+    env:
+      APP_ENV: opensearch
+    services:
+      opensearch:
+        image: opensearchproject/opensearch:${{ matrix.opensearch-version }}
+        ports:
+          - 9200:9200
+        env:
+          discovery.type: single-node
+          DISABLE_SECURITY_PLUGIN: 'true'
+          OPENSEARCH_INITIAL_ADMIN_PASSWORD: 'Admin_1234!'
+        options: >-
+          --health-cmd "curl -f http://localhost:9200/_cluster/health || exit 1"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 10
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          tools: pecl, composer
+          extensions: ${{ matrix.extensions }}
+          coverage: none
+          ini-values: memory_limit=-1
+      - name: Get composer cache directory
+        id: composercache
+        run: echo "dir=$(composer config cache-files-dir)" >> $GITHUB_OUTPUT
+      - name: Cache dependencies
+        uses: actions/cache@v5
+        with:
+          path: ${{ steps.composercache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.json') }}
+          restore-keys: ${{ runner.os }}-composer-
+      - name: Update project dependencies
+        run: |
+          composer global require soyuka/pmu
+          composer global config allow-plugins.soyuka/pmu true --no-interaction
+          composer global link .
+          composer require --dev opensearch-project/opensearch-php "^2.5" -W
+      - name: Clear test app cache
+        run: tests/Fixtures/app/console cache:clear --ansi
+      - name: Run Behat tests
+        run: vendor/bin/behat --out=std --format=progress --profile=opensearch --no-interaction
+
   phpunit-no-deprecations:
     name: PHPUnit (PHP ${{ matrix.php }}) (no deprecations)
     runs-on: ubuntu-latest
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 71298e7280b..6ccf07834e7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Features
+
+* [f74d7ba1a](https://github.com/api-platform/core/commit/f74d7ba1a) feat(elasticsearch): add OpenSearch support (#7519)
+
 ## v4.3.0-alpha.2
 
 ### Bug fixes
diff --git a/behat.yml.dist b/behat.yml.dist
index 5f7419cf8c0..c96ba8d3a43 100644
--- a/behat.yml.dist
+++ b/behat.yml.dist
@@ -107,6 +107,21 @@ elasticsearch:
       filters:
         tags: '@elasticsearch&&~@mercure&&~@query_parameter_validator'
 
+opensearch:
+  suites:
+    default: false
+    opensearch:
+      paths:
+        - '%paths.base%/features/elasticsearch'
+      contexts:
+        - 'ApiPlatform\Tests\Behat\CommandContext'
+        - 'ApiPlatform\Tests\Behat\ElasticsearchContext'
+        - 'ApiPlatform\Tests\Behat\JsonContext'
+        - 'Behat\MinkExtension\Context\MinkContext'
+        - 'behatch:context:rest'
+      filters:
+        tags: '@elasticsearch&&~@mercure&&~@query_parameter_validator'
+
 default-coverage:
   suites:
     default: &default-coverage-suite
diff --git a/composer.json b/composer.json
index 6f1c9c3dde5..0b922b61b16 100644
--- a/composer.json
+++ b/composer.json
@@ -202,6 +202,7 @@
     "suggest": {
         "doctrine/mongodb-odm-bundle": "To support MongoDB. Only versions 4.0 and later are supported.",
         "elasticsearch/elasticsearch": "To support Elasticsearch.",
+        "opensearch-project/opensearch-php": "To support OpenSearch (^2.5).",
         "phpstan/phpdoc-parser": "To support extracting metadata from PHPDoc.",
         "psr/cache-implementation": "To use metadata caching.",
         "ramsey/uuid": "To support Ramsey's UUID identifiers.",
diff --git a/src/Elasticsearch/State/CollectionProvider.php b/src/Elasticsearch/State/CollectionProvider.php
index df84a52e32d..4e78be7fa66 100644
--- a/src/Elasticsearch/State/CollectionProvider.php
+++ b/src/Elasticsearch/State/CollectionProvider.php
@@ -26,6 +26,8 @@
 use Elastic\Elasticsearch\Response\Elasticsearch;
 use Elasticsearch\Client as V7Client;
 use Elasticsearch\Common\Exceptions\Missing404Exception as V7Missing404Exception;
+use OpenSearch\Client as OpenSearchClient;
+use OpenSearch\Common\Exceptions\Missing404Exception as OpenSearchMissing404Exception;
 use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;
 
 /**
@@ -40,7 +42,7 @@ final class CollectionProvider implements ProviderInterface
      * @param RequestBodySearchCollectionExtensionInterface[] $collectionExtensions
      */
     public function __construct(
-        private readonly V7Client|Client $client, // @phpstan-ignore-line
+        private readonly V7Client|Client|OpenSearchClient $client, // @phpstan-ignore-line
         private readonly ?DenormalizerInterface $denormalizer = null,
         private readonly ?Pagination $pagination = null,
         private readonly iterable $collectionExtensions = [],
@@ -76,7 +78,7 @@ public function provide(Operation $operation, array $uriVariables = [], array $c
 
         try {
             $documents = $this->client->search($params); // @phpstan-ignore-line
-        } catch (V7Missing404Exception $e) { // @phpstan-ignore-line
+        } catch (V7Missing404Exception|OpenSearchMissing404Exception $e) { // @phpstan-ignore-line
             throw new Error(status: $e->getCode(), detail: $e->getMessage(), title: $e->getMessage(), originalTrace: $e->getTrace()); // @phpstan-ignore-line
         } catch (ClientResponseException $e) {
             $response = $e->getResponse();
diff --git a/src/Elasticsearch/State/ItemProvider.php b/src/Elasticsearch/State/ItemProvider.php
index 49158ae547e..88321d26fa2 100644
--- a/src/Elasticsearch/State/ItemProvider.php
+++ b/src/Elasticsearch/State/ItemProvider.php
@@ -24,6 +24,8 @@
 use Elastic\Elasticsearch\Response\Elasticsearch;
 use Elasticsearch\Client as V7Client;
 use Elasticsearch\Common\Exceptions\Missing404Exception as V7Missing404Exception;
+use OpenSearch\Client as OpenSearchClient;
+use OpenSearch\Common\Exceptions\Missing404Exception as OpenSearchMissing404Exception;
 use Symfony\Component\Serializer\Normalizer\AbstractNormalizer;
 use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;
 
@@ -36,7 +38,7 @@
 final class ItemProvider implements ProviderInterface
 {
     public function __construct(
-        private readonly V7Client|Client $client, // @phpstan-ignore-line
+        private readonly V7Client|Client|OpenSearchClient $client, // @phpstan-ignore-line
         private readonly ?DenormalizerInterface $denormalizer = null,
         private readonly ?InflectorInterface $inflector = new Inflector(),
     ) {
@@ -60,7 +62,7 @@ public function provide(Operation $operation, array $uriVariables = [], array $c
 
         try {
             $document = $this->client->get($params); // @phpstan-ignore-line
-        } catch (V7Missing404Exception) { // @phpstan-ignore-line
+        } catch (V7Missing404Exception|OpenSearchMissing404Exception) { // @phpstan-ignore-line
             return null;
         } catch (ClientResponseException $e) {
             $response = $e->getResponse();
diff --git a/src/Elasticsearch/composer.json b/src/Elasticsearch/composer.json
index 82ee303920f..9c59704a885 100644
--- a/src/Elasticsearch/composer.json
+++ b/src/Elasticsearch/composer.json
@@ -36,6 +36,9 @@
         "symfony/type-info": "^7.3 || ^8.0",
         "symfony/uid": "^6.4 || ^7.0 || ^8.0"
     },
+    "suggest": {
+        "opensearch-project/opensearch-php": "Required to use OpenSearch instead of Elasticsearch (^2.5)"
+    },
     "require-dev": {
         "phpspec/prophecy-phpunit": "^2.2",
         "phpunit/phpunit": "^12.2"
diff --git a/src/Symfony/Bundle/DependencyInjection/ApiPlatformExtension.php b/src/Symfony/Bundle/DependencyInjection/ApiPlatformExtension.php
index 42b625cf8ee..da27c443f5c 100644
--- a/src/Symfony/Bundle/DependencyInjection/ApiPlatformExtension.php
+++ b/src/Symfony/Bundle/DependencyInjection/ApiPlatformExtension.php
@@ -991,16 +991,21 @@ private function registerElasticsearchConfiguration(ContainerBuilder $container,
             throw new \LogicException('Elasticsearch support cannot be enabled as the Elasticsearch component is not installed. Try running "composer require api-platform/elasticsearch".');
         }
 
-        $clientClass = !class_exists(\Elasticsearch\Client::class)
-            // ES v7
-            ? \Elastic\Elasticsearch\Client::class
+        if ('opensearch' === $config['elasticsearch']['client']) {
+            $clientClass = \OpenSearch\Client::class; // @phpstan-ignore class.notFound
+        } elseif (!class_exists(\Elasticsearch\Client::class)) {
             // ES v8 and up
-            : \Elasticsearch\Client::class;
+            $clientClass = \Elastic\Elasticsearch\Client::class;
+        } else {
+            // ES v7
+            $clientClass = \Elasticsearch\Client::class;
+        }
 
         $clientDefinition = new Definition($clientClass);
         $container->setDefinition('api_platform.elasticsearch.client', $clientDefinition);
         $container->registerForAutoconfiguration(RequestBodySearchCollectionExtensionInterface::class)
             ->addTag('api_platform.elasticsearch.request_body_search_extension.collection');
+        $container->setParameter('api_platform.elasticsearch.client', $config['elasticsearch']['client']);
         $container->setParameter('api_platform.elasticsearch.hosts', $config['elasticsearch']['hosts']);
         $container->setParameter('api_platform.elasticsearch.ssl_ca_bundle', $config['elasticsearch']['ssl_ca_bundle']);
         $container->setParameter('api_platform.elasticsearch.ssl_verification', $config['elasticsearch']['ssl_verification']);
diff --git a/src/Symfony/Bundle/DependencyInjection/Compiler/ElasticsearchClientPass.php b/src/Symfony/Bundle/DependencyInjection/Compiler/ElasticsearchClientPass.php
index 7a429febe1f..d676c46866f 100644
--- a/src/Symfony/Bundle/DependencyInjection/Compiler/ElasticsearchClientPass.php
+++ b/src/Symfony/Bundle/DependencyInjection/Compiler/ElasticsearchClientPass.php
@@ -39,7 +39,9 @@ public function process(ContainerBuilder $container): void
             $clientConfiguration['hosts'] = $hosts;
         }
 
-        if (class_exists(\Elasticsearch\ClientBuilder::class)) {
+        if ('opensearch' === $container->getParameter('api_platform.elasticsearch.client')) {
+            $builderName = \OpenSearch\ClientBuilder::class; // @phpstan-ignore class.notFound
+        } elseif (class_exists(\Elasticsearch\ClientBuilder::class)) {
             // ES v7
             $builderName = \Elasticsearch\ClientBuilder::class;
         } else {
diff --git a/src/Symfony/Bundle/DependencyInjection/Configuration.php b/src/Symfony/Bundle/DependencyInjection/Configuration.php
index 43954615e50..b5ecf65fa8a 100644
--- a/src/Symfony/Bundle/DependencyInjection/Configuration.php
+++ b/src/Symfony/Bundle/DependencyInjection/Configuration.php
@@ -505,8 +505,10 @@ private function addElasticsearchSection(ArrayNodeDefinition $rootNode): void
                                         !class_exists(\Elasticsearch\Client::class)
                                         // ES v8 and up
                                         && !class_exists(\Elastic\Elasticsearch\Client::class)
+                                        // OpenSearch
+                                        && !class_exists(\OpenSearch\Client::class)
                                     ) {
-                                        throw new InvalidConfigurationException('The elasticsearch/elasticsearch package is required for Elasticsearch support.');
+                                        throw new InvalidConfigurationException('The elasticsearch/elasticsearch or opensearch-project/opensearch-php package is required for Elasticsearch support.');
                                     }
 
                                     return $v;
@@ -526,6 +528,21 @@ private function addElasticsearchSection(ArrayNodeDefinition $rootNode): void
                             ->defaultTrue()
                             ->info('Enable or disable SSL verification for Elasticsearch connections.')
                         ->end()
+                        ->enumNode('client')
+                            ->values(['elasticsearch', 'opensearch'])
+                            ->defaultValue('elasticsearch')
+                            ->info('The search engine client to use: "elasticsearch" or "opensearch".')
+                            ->validate()
+                                ->ifString()
+                                ->then(static function (string $v): string {
+                                    if ('opensearch' === $v && !class_exists(\OpenSearch\Client::class)) {
+                                        throw new InvalidConfigurationException('Setting api_platform.elasticsearch.client to "opensearch" requires the opensearch-project/opensearch-php package. Try running "composer require opensearch-project/opensearch-php".');
+                                    }
+
+                                    return $v;
+                                })
+                            ->end()
+                        ->end()
                     ->end()
                 ->end()
             ->end();
diff --git a/tests/Behat/ElasticsearchContext.php b/tests/Behat/ElasticsearchContext.php
index 5c8c2debb95..cc8fa176b67 100644
--- a/tests/Behat/ElasticsearchContext.php
+++ b/tests/Behat/ElasticsearchContext.php
@@ -16,6 +16,7 @@
 use Behat\Behat\Context\Context;
 use Elastic\Elasticsearch\Client;
 use Elasticsearch\Client as V7Client;
+use OpenSearch\Client as OpenSearchClient;
 use Symfony\Component\Finder\Finder;
 
 /**
@@ -26,7 +27,7 @@
 final class ElasticsearchContext implements Context
 {
     public function __construct(
-        private readonly V7Client|Client $client, // @phpstan-ignore-line
+        private readonly V7Client|Client|OpenSearchClient $client, // @phpstan-ignore-line
         private readonly string $elasticsearchMappingsPath,
         private readonly string $elasticsearchFixturesPath,
     ) {
diff --git a/tests/Fixtures/app/config/config_opensearch.yml b/tests/Fixtures/app/config/config_opensearch.yml
new file mode 100644
index 00000000000..66c518f9503
--- /dev/null
+++ b/tests/Fixtures/app/config/config_opensearch.yml
@@ -0,0 +1,27 @@
+imports:
+    - { resource: config_common.yml }
+    - { resource: config_behat_orm.yml }
+
+parameters:
+    env(ELASTICSEARCH_URL): http://localhost:9200
+
+api_platform:
+    doctrine: false
+    mapping:
+        paths:
+            - '%kernel.project_dir%/../Elasticsearch/Model'
+    elasticsearch:
+        hosts: '%env(resolve:ELASTICSEARCH_URL)%'
+        client: opensearch
+
+services:
+    test.api_platform.elasticsearch.client:
+        parent: api_platform.elasticsearch.client
+        public: true
+
+    ApiPlatform\Tests\Behat\ElasticsearchContext:
+        public: true
+        arguments:
+            $client: '@test.api_platform.elasticsearch.client'
+            $elasticsearchMappingsPath: '%kernel.project_dir%/../Elasticsearch/Mappings/'
+            $elasticsearchFixturesPath: '%kernel.project_dir%/../Elasticsearch/Fixtures/'
diff --git a/tests/Fixtures/app/config/routing_opensearch.yml b/tests/Fixtures/app/config/routing_opensearch.yml
new file mode 100644
index 00000000000..eae54ec1b02
--- /dev/null
+++ b/tests/Fixtures/app/config/routing_opensearch.yml
@@ -0,0 +1,2 @@
+_main:
+    resource: routing.yml
diff --git a/tests/Symfony/Bundle/DependencyInjection/Compiler/ElasticsearchClientPassTest.php b/tests/Symfony/Bundle/DependencyInjection/Compiler/ElasticsearchClientPassTest.php
index 70e954540ee..12ced7b3662 100644
--- a/tests/Symfony/Bundle/DependencyInjection/Compiler/ElasticsearchClientPassTest.php
+++ b/tests/Symfony/Bundle/DependencyInjection/Compiler/ElasticsearchClientPassTest.php
@@ -68,6 +68,7 @@ public function testProcess(): void
 
         $containerBuilderProphecy = $this->prophesize(ContainerBuilder::class);
         $containerBuilderProphecy->getParameter('api_platform.elasticsearch.enabled')->willReturn(true)->shouldBeCalled();
+        $containerBuilderProphecy->getParameter('api_platform.elasticsearch.client')->willReturn('elasticsearch')->shouldBeCalled();
         $containerBuilderProphecy->getParameter('api_platform.elasticsearch.hosts')->willReturn(['http://localhost:9200'])->shouldBeCalled();
         $containerBuilderProphecy->getParameter('api_platform.elasticsearch.ssl_ca_bundle')->willReturn(null)->shouldBeCalled();
         $containerBuilderProphecy->getParameter('api_platform.elasticsearch.ssl_verification')->willReturn(true)->shouldBeCalled();
@@ -77,6 +78,53 @@ public function testProcess(): void
         (new ElasticsearchClientPass())->process($containerBuilderProphecy->reveal());
     }
 
+    public function testProcessWithOpenSearchClient(): void
+    {
+        if (!class_exists(\OpenSearch\ClientBuilder::class)) {
+            self::markTestSkipped('opensearch-project/opensearch-php is not installed.');
+        }
+
+        $clientDefinition = $this->createMock(Definition::class);
+        $clientDefinition->expects($this->once())
+            ->method('setFactory')
+            ->with([\OpenSearch\ClientBuilder::class, 'fromConfig'])
+            ->willReturnSelf();
+
+        $clientDefinition->expects($this->once())
+            ->method('setArguments')
+            ->with($this->callback(static function ($arguments) {
+                $config = $arguments[0];
+
+                return isset($config['hosts'])
+                    && $config['hosts'] === ['http://localhost:9200']
+                    && isset($config['logger'])
+                    && $config['logger'] instanceof Reference;
+            }))
+            ->willReturnSelf();
+
+        $containerBuilder = $this->createMock(ContainerBuilder::class);
+        $containerBuilder->method('getParameter')
+            ->willReturnMap([
+                ['api_platform.elasticsearch.enabled', true],
+                ['api_platform.elasticsearch.client', 'opensearch'],
+                ['api_platform.elasticsearch.hosts', ['http://localhost:9200']],
+                ['api_platform.elasticsearch.ssl_ca_bundle', null],
+                ['api_platform.elasticsearch.ssl_verification', true],
+            ]);
+
+        $containerBuilder->expects($this->once())
+            ->method('has')
+            ->with('logger')
+            ->willReturn(true);
+
+        $containerBuilder->expects($this->once())
+            ->method('getDefinition')
+            ->with('api_platform.elasticsearch.client')
+            ->willReturn($clientDefinition);
+
+        (new ElasticsearchClientPass())->process($containerBuilder);
+    }
+
     public function testProcessWithoutConfiguration(): void
     {
         $clientBuilder = class_exists(\Elasticsearch\ClientBuilder::class)
@@ -90,6 +138,7 @@ public function testProcessWithoutConfiguration(): void
 
         $containerBuilderProphecy = $this->prophesize(ContainerBuilder::class);
         $containerBuilderProphecy->getParameter('api_platform.elasticsearch.enabled')->willReturn(true)->shouldBeCalled();
+        $containerBuilderProphecy->getParameter('api_platform.elasticsearch.client')->willReturn('elasticsearch')->shouldBeCalled();
         $containerBuilderProphecy->getParameter('api_platform.elasticsearch.hosts')->willReturn([])->shouldBeCalled();
         $containerBuilderProphecy->getParameter('api_platform.elasticsearch.ssl_ca_bundle')->willReturn(null)->shouldBeCalled();
         $containerBuilderProphecy->getParameter('api_platform.elasticsearch.ssl_verification')->willReturn(true)->shouldBeCalled();
@@ -139,6 +188,7 @@ public function testProcessWithSslCaBundle(): void
         $containerBuilder->method('getParameter')
             ->willReturnMap([
                 ['api_platform.elasticsearch.enabled', true],
+                ['api_platform.elasticsearch.client', 'elasticsearch'],
                 ['api_platform.elasticsearch.hosts', ['https://localhost:9200']],
                 ['api_platform.elasticsearch.ssl_ca_bundle', '/path/to/ca-bundle.crt'],
                 ['api_platform.elasticsearch.ssl_verification', true],
@@ -187,6 +237,7 @@ public function testProcessWithSslVerificationDisabled(): void
         $containerBuilder->method('getParameter')
             ->willReturnMap([
                 ['api_platform.elasticsearch.enabled', true],
+                ['api_platform.elasticsearch.client', 'elasticsearch'],
                 ['api_platform.elasticsearch.hosts', ['https://localhost:9200']],
                 ['api_platform.elasticsearch.ssl_ca_bundle', null],
                 ['api_platform.elasticsearch.ssl_verification', false],
diff --git a/tests/Symfony/Bundle/DependencyInjection/ConfigurationTest.php b/tests/Symfony/Bundle/DependencyInjection/ConfigurationTest.php
index 52b3d33f3fa..def95beb140 100644
--- a/tests/Symfony/Bundle/DependencyInjection/ConfigurationTest.php
+++ b/tests/Symfony/Bundle/DependencyInjection/ConfigurationTest.php
@@ -141,6 +141,7 @@ private function runDefaultConfigTests(array $doctrineIntegrationsToLoad = ['orm
                 'hosts' => [],
                 'ssl_ca_bundle' => null,
                 'ssl_verification' => true,
+                'client' => 'elasticsearch',
             ],
             'oauth' => [
                 'enabled' => false,
@@ -489,6 +490,25 @@ public function testElasticsearchSslVerificationDisabled(): void
         $this->assertNull($config['elasticsearch']['ssl_ca_bundle']);
     }
 
+    public function testElasticsearchOpenSearchClientRequiresPackage(): void
+    {
+        if (class_exists(\OpenSearch\Client::class)) {
+            self::markTestSkipped('opensearch-project/opensearch-php is installed.');
+        }
+
+        $this->expectException(InvalidConfigurationException::class);
+        $this->expectExceptionMessage('Setting api_platform.elasticsearch.client to "opensearch" requires the opensearch-project/opensearch-php package.');
+
+        $this->processor->processConfiguration($this->configuration, [
+            'api_platform' => [
+                'elasticsearch' => [
+                    'enabled' => true,
+                    'client' => 'opensearch',
+                ],
+            ],
+        ]);
+    }
+
     public function testElasticsearchSslCaBundleAndVerificationDisabledMutuallyExclusive(): void
     {
         $this->expectException(InvalidConfigurationException::class);