diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 0badf81..e153a5d 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -41,6 +41,7 @@ jobs:
                     php-version: "${{ matrix.php-version }}"
                     extensions: "${{ env.PHP_EXTENSIONS }}"
                     coverage: "none"
+                    tools: "symfony"
 
             -   name: "Install composer dependencies"
                 uses: "ramsey/composer-install@v3"
@@ -65,6 +66,9 @@ jobs:
             -   name: "Lint twig files"
                 run: "(cd tests/Application && bin/console lint:twig ../../src/Resources)"
 
+            -   name: "Symfony diagnostics"
+                run: "symfony lsp:check --format=github"
+
     dependency-analysis:
         name: "Dependency Analysis (PHP${{ matrix.php-version }} | Deps: ${{ matrix.dependencies }} | SF${{ matrix.symfony }})"
 
diff --git a/.gitignore b/.gitignore
index 4899dfc..dfcf9ef 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,6 +8,9 @@
 /.phpunit.cache/
 /.phpunit.result.cache
 
+# symfony lsp:check analyzes the repository root and caches in var/symfony-lsp
+/var/
+
 # Symfony CLI https://symfony.com/doc/current/setup/symfony_server.html#different-php-settings-per-project
 /.php-version
 /php.ini
diff --git a/.symfony-lsp.json b/.symfony-lsp.json
new file mode 100644
index 0000000..1b2add6
--- /dev/null
+++ b/.symfony-lsp.json
@@ -0,0 +1,8 @@
+{
+    "version": 1,
+    "projectRoots": [
+        "."
+    ],
+    "kernel": "Acme\\SyliusExamplePlugin\\Tests\\Application\\Kernel",
+    "translationDiagnostics": true
+}
diff --git a/CLAUDE.md b/CLAUDE.md
index 156be9f..9d251f0 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -41,6 +41,7 @@ Based on the `composer.json` scripts section:
 - `composer check-style` - Check code style with ECS (Easy Coding Standard)
 - `composer fix-style` - Fix code style issues automatically with ECS
 - `composer phpunit` - Run PHPUnit tests
+- `symfony lsp:check` - Run Symfony-aware diagnostics (routes, services, templates, translations, config) against the plugin and its test application. Requires the Symfony CLI 5.20 or newer
 
 ### Static Analysis
 
diff --git a/tests/Application/config/packages/framework.yaml b/tests/Application/config/packages/framework.yaml
index 3df2c0a..753cd81 100644
--- a/tests/Application/config/packages/framework.yaml
+++ b/tests/Application/config/packages/framework.yaml
@@ -1,9 +1,14 @@
+parameters:
+    # Adds a fallback APP_SECRET if the env var is not set, like DATABASE_URL in doctrine.yaml. symfony lsp:check
+    # analyzes the repository root and only loads a .env file from there, so it boots the kernel without
+    # tests/Application/.env
+    env(APP_SECRET): 'EDITME'
+
 framework:
     secret: '%env(APP_SECRET)%'
     ide: phpstorm
     form:
         enabled: true
-        legacy_error_messages: false
     csrf_protection: true
     session:
         handler_id: ~
diff --git a/tests/Application/config/packages/security.yaml b/tests/Application/config/packages/security.yaml
index 2f5c687..a070ffb 100644
--- a/tests/Application/config/packages/security.yaml
+++ b/tests/Application/config/packages/security.yaml
@@ -1,5 +1,4 @@
 security:
-    enable_authenticator_manager: true
     providers:
         sylius_admin_user_provider:
             id: sylius.admin_user_provider.email_or_name_based