diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d3041b9..20a58b8 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -17,7 +17,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php: [ '8.1', '8.2', '8.3', '8.4' ]
+        php: [ '8.2', '8.3', '8.4', '8.5' ]
         ext_base: [ 'none, dom, tokenizer, xml, xmlwriter,' ]
         ext_lib: [ 'curl, mbstring, openssl,' ]
         ext_optional: [ '', 'bcmath', 'gmp' ]
@@ -43,8 +43,8 @@ jobs:
         uses: actions/cache@v4
         with:
           path: ${{ steps.composer-cache.outputs.dir }}
-          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
-          restore-keys: ${{ runner.os }}-composer-
+          key: ${{ runner.os }}-composer-php${{ matrix.php }}-${{ matrix.ext_optional }}-${{ hashFiles('**/composer.json') }}
+          restore-keys: ${{ runner.os }}-composer-php${{ matrix.php }}-${{ matrix.ext_optional }}
 
       - name: Install dependencies
         run: composer install --prefer-dist
@@ -52,7 +52,7 @@ jobs:
       - name: Setup node
         uses: actions/setup-node@v6
         with:
-          node-version: '20'
+          node-version: '24'
 
       - name: Install web-push-testing server
         run: |
diff --git a/.php-cs-fixer.php b/.php-cs-fixer.php
index e041068..e68ada2 100644
--- a/.php-cs-fixer.php
+++ b/.php-cs-fixer.php
@@ -4,7 +4,7 @@
 $config = new PhpCsFixer\Config();
 $rules  = [
     '@PSR12'                              => true, // The default rule.
-    '@PHP81Migration'                     => true, // Must be the same as the min PHP version.
+    '@autoPHPMigration'                   => true, // Uses min PHP version for regular migrations.
     'blank_line_after_opening_tag'        => false, // Do not waste space between <?php and declare.
     'global_namespace_import'             => ['import_classes' => false, 'import_constants' => false, 'import_functions' => false],
     'php_unit_construct'                  => true,
@@ -12,8 +12,8 @@
     'php_unit_method_casing'              => true,
     'php_unit_test_class_requires_covers' => true,
     // Do not enable by default. These rules require review!! (but they are useful)
-    // '@PHP80Migration:risky'      => true,
-    // '@PHPUnit100Migration:risky' => true,
+    // '@autoPHPMigration:risky'      => true,
+    // '@autoPHPUnitMigration:risky' => true,
 ];
 
 $config->setRules($rules);
diff --git a/README.md b/README.md
index c849a1e..162f280 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ This push message is then received by the browser, which can then create a notif
 
 ## Requirements
 
-PHP 8.1+ and the following extensions:
+PHP 8.2+ and the following extensions:
 
 - bcmath and/or gmp (optional but better for performance)
 - mbstring
@@ -25,6 +25,7 @@ There is no support and maintenance for older PHP versions, however you are free
 - PHP 7.2: `v6.x`
 - PHP 7.3 7.4: `v7.x`
 - PHP 8.0 / Openssl without elliptic curve support: `v8.x`
+- PHP 8.1: `v9.x`
 
 This README is only compatible with the latest version. Each version of the library has a git tag where the corresponding README can be read.
 
diff --git a/composer.json b/composer.json
index 5d85c39..9d99abb 100644
--- a/composer.json
+++ b/composer.json
@@ -28,23 +28,22 @@
     "test:syntax_tests": "./vendor/bin/php-cs-fixer fix ./tests --dry-run --stop-on-violation --using-cache=no"
   },
   "require": {
-    "php": ">=8.1",
+    "php": ">=8.2",
     "ext-curl": "*",
     "ext-json": "*",
     "ext-mbstring": "*",
     "ext-openssl": "*",
     "guzzlehttp/guzzle": "^7.9.2",
     "spomky-labs/base64url": "^2.0.4",
-    "symfony/polyfill-php82": "^v1.31.0",
-    "web-token/jwt-library": "^3.3.0|^4.0.0"
+    "web-token/jwt-library": "^3.4.9|^4.0.6"
   },
   "suggest": {
     "ext-bcmath": "Optional for performance.",
     "ext-gmp": "Optional for performance."
   },
   "require-dev": {
-    "phpunit/phpunit": "^10.5.44|^11.5.6",
-    "phpstan/phpstan": "^2.1.2",
+    "phpunit/phpunit": "^11.5.46|^12.5.2",
+    "phpstan/phpstan": "^2.1.33",
     "friendsofphp/php-cs-fixer": "^v3.91.3",
     "symfony/polyfill-iconv": "^1.33"
   },
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index bcff581..b6195bf 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -4,10 +4,15 @@
          bootstrap="vendor/autoload.php"
          cacheDirectory=".phpunit.cache"
          colors="true"
+         displayDetailsOnPhpunitDeprecations="true"
+         displayDetailsOnTestsThatTriggerDeprecations="true"
+         displayDetailsOnTestsThatTriggerErrors="true"
+         displayDetailsOnTestsThatTriggerNotices="true"
+         displayDetailsOnTestsThatTriggerWarnings="true"
          processIsolation="false"
          stopOnFailure="false"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/11.5/phpunit.xsd"
 >
     <source ignoreSuppressionOfDeprecations="true"
             ignoreSuppressionOfPhpDeprecations="true"
diff --git a/src/Encryption.php b/src/Encryption.php
index 0f58e6e..5e7366b 100644
--- a/src/Encryption.php
+++ b/src/Encryption.php
@@ -296,7 +296,7 @@ private static function calculateAgreementKey(JWK $private_key, JWK $public_key)
         $publicPem = ECKey::convertPublicKeyToPEM($public_key);
         $privatePem = ECKey::convertPrivateKeyToPEM($private_key);
 
-        $result = openssl_pkey_derive($publicPem, $privatePem, 256);
+        $result = openssl_pkey_derive($publicPem, $privatePem);
         if ($result === false) {
             throw new \RuntimeException('Unable to compute the agreement key.');
         }
diff --git a/src/WebPush.php b/src/WebPush.php
index 80c74b3..9b70544 100644
--- a/src/WebPush.php
+++ b/src/WebPush.php
@@ -157,9 +157,7 @@ public function flush(?int $batchSize = null): \Generator
                         /** @var ResponseInterface $response **/
                         return new MessageSentReport($request, $response);
                     })
-                    ->otherwise(function ($reason) {
-                        return $this->createRejectedReport($reason);
-                    });
+                    ->otherwise(fn ($reason) => $this->createRejectedReport($reason));
             }
 
             foreach ($promises as $promise) {
@@ -200,12 +198,12 @@ public function flushPooled($callback, ?int $batchSize = null, ?int $requestConc
             $batch = $this->prepare($batch);
             $pool = new Pool($this->client, $batch, [
                 'concurrency' => $requestConcurrency,
-                'fulfilled' => function (ResponseInterface $response, int $index) use ($callback, $batch) {
+                'fulfilled' => function (ResponseInterface $response, int $index) use ($callback, $batch): void {
                     /** @var RequestInterface $request **/
                     $request = $batch[$index];
                     $callback(new MessageSentReport($request, $response));
                 },
-                'rejected' => function ($reason) use ($callback) {
+                'rejected' => function ($reason) use ($callback): void {
                     $callback($this->createRejectedReport($reason));
                 },
             ]);
diff --git a/tests/PushServiceTest.php b/tests/PushServiceTest.php
index 805f4c4..b3be757 100644
--- a/tests/PushServiceTest.php
+++ b/tests/PushServiceTest.php
@@ -166,7 +166,6 @@ private function getResponse($ch)
 
         if (!$resp) {
             $error = 'Curl error: n'.curl_errno($ch).' - '.curl_error($ch);
-            curl_close($ch);
             throw new RuntimeException($error);
         }
 
@@ -176,9 +175,6 @@ private function getResponse($ch)
             throw new RuntimeException('web-push-testing-service error: '.$resp);
         }
 
-        // Close request to clear up some resources
-        curl_close($ch);
-
         return $parsedResp;
     }
 }
diff --git a/tests/WebPushTest.php b/tests/WebPushTest.php
index 0f9f461..aed4b3c 100644
--- a/tests/WebPushTest.php
+++ b/tests/WebPushTest.php
@@ -107,7 +107,6 @@ private static function setCiEnvironment(): void
 
         if (!$response) {
             $error = 'Curl error: n'.curl_errno($getSubscriptionCurl).' - '.curl_error($getSubscriptionCurl);
-            curl_close($getSubscriptionCurl);
             throw new RuntimeException($error);
         }
 
@@ -248,7 +247,7 @@ public function testFlushPooled(): void
         $this->webPush->queueNotification($nonExistentSubscription, json_encode(['test' => 2], JSON_THROW_ON_ERROR));
         $this->webPush->queueNotification($nonExistentSubscription, json_encode(['test' => 3], JSON_THROW_ON_ERROR));
 
-        $callback = function ($report) {
+        $callback = function ($report): void {
             $this->assertFalse($report->isSuccess());
             $this->assertTrue($report->isSubscriptionExpired());
             $this->assertEquals(410, $report->getResponse()->getStatusCode());