diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9cef46e..08c9502 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -10,12 +10,12 @@ jobs:
       fail-fast: false
       matrix:
         operating-system: [ ubuntu-latest ]
-        php-versions: [ '8.1' ]
+        php-versions: [ '8.2' ]
 
     runs-on: ubuntu-latest
     steps:
       # —— Github Checkout 🔎 ——————————————————————————————————————————————————
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
@@ -37,18 +37,25 @@ jobs:
       fail-fast: false
       matrix:
         operating-system: [ubuntu-latest]
-        php-versions: [ '7.4', '8.0', '8.1' ]
-        symfony: [ '5.4', '6.0' ]
+        php-versions: [ '8.2', '8.3', '8.4', '8.5' ]
+        symfony: [ '6.4', '7.4', '8.0', '8.1' ]
         exclude:
-          - php-versions: '7.4'
-            symfony: '6.0'
+          # Symfony 8.x requires PHP >= 8.4
+          - php-versions: '8.2'
+            symfony: '8.0'
+          - php-versions: '8.3'
+            symfony: '8.0'
+          - php-versions: '8.2'
+            symfony: '8.1'
+          - php-versions: '8.3'
+            symfony: '8.1'
 
     runs-on: ${{ matrix.operating-system }}
 
     steps:
         # —— Git Checkout PR branch ——————————————————————————————————————————
       - name: Git Checkout PR branch (${{ github.ref }})
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
@@ -65,13 +72,13 @@ jobs:
       # —— Composer cache ————————————————————————————————————————————————————
       - name: Get composer cache directory
         id: composer-cache
-        run: echo "::set-output name=dir::$(composer config cache-files-dir)"
+        run: echo "dir=$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
 
       - name: Cache composer dependencies
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ${{ steps.composer-cache.outputs.dir }}
-          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          key: ${{ runner.os }}-composer-${{ matrix.php-versions }}-${{ matrix.symfony }}
           restore-keys: ${{ runner.os }}-composer-
 
       # —— Install composer dependencies —————————————————————————————————————
@@ -79,9 +86,10 @@ jobs:
         env:
           COMPOSER_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
         run: |
-          composer global require --no-interaction --no-progress symfony/flex:^1.11
+          composer global config --no-plugins allow-plugins.symfony/flex true
+          composer global require --no-interaction --no-progress symfony/flex
           composer config extra.symfony.require "${{ matrix.symfony }}.*"
-          composer install --no-progress --no-scripts -q
+          composer update --no-progress --no-scripts
 
 #      # —— PHPStan  ——————————————————————————————————————————————————————————
 #      - name: PHPStan (PHP Static Analysis)
diff --git a/composer.json b/composer.json
index a349b49..6f35611 100644
--- a/composer.json
+++ b/composer.json
@@ -14,17 +14,17 @@
     "php": "^8.2",
     "ext-json": "*",
     "phpdocumentor/reflection-docblock": "^5.3",
-    "symfony/debug-bundle": "^6.4|^7.0",
-    "symfony/http-client": "^6.4|^7.0",
-    "symfony/property-access": "^6.4|^7.0",
-    "symfony/property-info": "^6.4|^7.0",
-    "symfony/serializer": "^6.4|^7.0"
+    "symfony/debug-bundle": "^6.4|^7.4|^8.0",
+    "symfony/http-client": "^6.4|^7.4|^8.0",
+    "symfony/property-access": "^6.4|^7.4|^8.0",
+    "symfony/property-info": "^6.4|^7.4|^8.0",
+    "symfony/serializer": "^6.4|^7.4|^8.0"
   },
   "require-dev" : {
     "friendsofphp/php-cs-fixer": "^3.15",
     "phpstan/phpstan": "^1.8.7",
     "phpunit/phpunit": "^9.5|^10.0",
-    "symfony/var-dumper": "^6.4|^7.0"
+    "symfony/var-dumper": "^6.4|^7.4|^8.0"
   },
   "autoload": {
     "psr-4": {
diff --git a/src/Connection.php b/src/Connection.php
index dbbcbbf..2af8241 100644
--- a/src/Connection.php
+++ b/src/Connection.php
@@ -24,7 +24,7 @@ final class Connection
 
     private ?HttpClientInterface $client = null;
 
-    public function __construct(string $uri = null)
+    public function __construct(?string $uri = null)
     {
         if ($uri) {
             $this->uri = $uri;
diff --git a/src/Serializer/Normalizer/ArrivalNormalizer.php b/src/Serializer/Normalizer/ArrivalNormalizer.php
index d2c2ece..625247e 100644
--- a/src/Serializer/Normalizer/ArrivalNormalizer.php
+++ b/src/Serializer/Normalizer/ArrivalNormalizer.php
@@ -14,12 +14,12 @@ final class ArrivalNormalizer implements DenormalizerInterface
      *
      * @throws \Exception
      */
-    public function denormalize(mixed $data, string $type, string $format = null, array $context = []): \DateTimeImmutable
+    public function denormalize(mixed $data, string $type, ?string $format = null, array $context = []): \DateTimeImmutable
     {
         return DateTimeUtil::fromUTC(new \DateTimeImmutable('@'.$data));
     }
 
-    public function supportsDenormalization(mixed $data, string $type, string $format = null, array $context = []): bool
+    public function supportsDenormalization(mixed $data, string $type, ?string $format = null, array $context = []): bool
     {
         return 'DateTimeImmutable' === $type && is_int($data) && $data > 604800;
     }
diff --git a/src/Serializer/Normalizer/LocationNormalizer.php b/src/Serializer/Normalizer/LocationNormalizer.php
index 7a43fa7..7048399 100644
--- a/src/Serializer/Normalizer/LocationNormalizer.php
+++ b/src/Serializer/Normalizer/LocationNormalizer.php
@@ -13,7 +13,7 @@ final class LocationNormalizer implements NormalizerInterface, DenormalizerInter
     /**
      * @param Location $object
      */
-    public function normalize(mixed $object, string $format = null, array $context = []): array
+    public function normalize(mixed $object, ?string $format = null, array $context = []): array
     {
         return [
             $object->lon,
@@ -24,7 +24,7 @@ public function normalize(mixed $object, string $format = null, array $context =
     /**
      * @param Location $data
      */
-    public function supportsNormalization(mixed $data, string $format = null, array $context = []): bool
+    public function supportsNormalization(mixed $data, ?string $format = null, array $context = []): bool
     {
         return $data instanceof Location;
     }
@@ -32,7 +32,7 @@ public function supportsNormalization(mixed $data, string $format = null, array
     /**
      * @param array $data
      */
-    public function denormalize(mixed $data, string $type, string $format = null, array $context = []): Location
+    public function denormalize(mixed $data, string $type, ?string $format = null, array $context = []): Location
     {
         return new Location($data[0], $data[1]);
     }
@@ -40,7 +40,7 @@ public function denormalize(mixed $data, string $type, string $format = null, ar
     /**
      * @param array $data
      */
-    public function supportsDenormalization(mixed $data, string $type, string $format = null, array $context = []): bool
+    public function supportsDenormalization(mixed $data, string $type, ?string $format = null, array $context = []): bool
     {
         return Location::class === $type;
     }
diff --git a/src/Serializer/Normalizer/TimeWindowNormalizer.php b/src/Serializer/Normalizer/TimeWindowNormalizer.php
index e45cc61..2c3b599 100644
--- a/src/Serializer/Normalizer/TimeWindowNormalizer.php
+++ b/src/Serializer/Normalizer/TimeWindowNormalizer.php
@@ -15,7 +15,7 @@ final class TimeWindowNormalizer implements NormalizerInterface
     /**
      * @param TimeWindowInterface $object
      */
-    public function normalize(mixed $object, string $format = null, array $context = []): ?array
+    public function normalize(mixed $object, ?string $format = null, array $context = []): ?array
     {
         if ($object instanceof AbsoluteTimeWindow) {
             return [
@@ -37,7 +37,7 @@ public function normalize(mixed $object, string $format = null, array $context =
     /**
      * @param TimeWindowInterface $data
      */
-    public function supportsNormalization(mixed $data, string $format = null, array $context = []): bool
+    public function supportsNormalization(mixed $data, ?string $format = null, array $context = []): bool
     {
         return $data instanceof TimeWindowInterface;
     }