diff --git a/.appveyor.yml b/.appveyor.yml
index 02c594d300..a89445a65b 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -49,9 +49,8 @@ install:
     - git config --global user.email ""
     - git config --global user.name "Symfony"
     - FOR /F "tokens=* USEBACKQ" %%F IN (`bash -c "grep branch-version composer.json | grep -o '[0-9.x]*'"`) DO (SET SYMFONY_VERSION=%%F)
-    - php .github/build-packages.php "HEAD^" %SYMFONY_VERSION% src\Symfony\Bridge\PhpUnit src\Symfony\Contracts
+    - php .github/build-packages.php HEAD^ %SYMFONY_VERSION% src\Symfony\Bridge\PhpUnit
     - SET "SYMFONY_REQUIRE=>=%SYMFONY_VERSION%"
-    - SET COMPOSER_ROOT_VERSION=%SYMFONY_VERSION%.x-dev
     - php composer.phar update --no-progress --ansi
     - php phpunit install
 
diff --git a/.github/build-packages.php b/.github/build-packages.php
index 13978ab4e6..c8c802ad59 100644
--- a/.github/build-packages.php
+++ b/.github/build-packages.php
@@ -6,17 +6,12 @@ if (3 > $_SERVER['argc']) {
 }
 chdir(dirname(__DIR__));
 
-$json = ltrim(file_get_contents('composer.json'));
-if ($json !== $package = preg_replace('/\n    "repositories": \[\n.*?\n    \],/s', '', $json)) {
-    file_put_contents('composer.json', $package);
-}
-
 $dirs = $_SERVER['argv'];
 array_shift($dirs);
 $mergeBase = trim(shell_exec(sprintf('git merge-base "%s" HEAD', array_shift($dirs))));
 $version = array_shift($dirs);
 
-$packages = array();
+$packages = [];
 $flags = JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE;
 $preferredInstall = json_decode(file_get_contents(__DIR__.'/composer-config.json'), true)['config']['preferred-install'];
 
@@ -36,12 +31,12 @@ foreach ($dirs as $k => $dir) {
         exit(1);
     }
 
-    $package->repositories = array(array(
+    $package->repositories = [[
         'type' => 'composer',
         'url' => 'file://'.str_replace(DIRECTORY_SEPARATOR, '/', dirname(__DIR__)).'/',
-    ));
+    ]];
     if (false === strpos($json, "\n    \"repositories\": [\n")) {
-        $json = rtrim(json_encode(array('repositories' => $package->repositories), $flags), "\n}").','.substr($json, 1);
+        $json = rtrim(json_encode(['repositories' => $package->repositories], $flags), "\n}").','.substr($json, 1);
         file_put_contents($dir.'/composer.json', $json);
     }
 
@@ -61,7 +56,7 @@ foreach ($dirs as $k => $dir) {
     $versions = json_decode($versions)->packages->{$package->name};
 
     foreach ($versions as $v => $package) {
-        $packages[$package->name] += array($v => $package);
+        $packages[$package->name] += [$v => $package];
     }
 }
 
@@ -74,10 +69,12 @@ if ($dirs) {
         exit(1);
     }
 
-    $package->repositories = array(array(
+    $package->repositories[] = [
         'type' => 'composer',
         'url' => 'file://'.str_replace(DIRECTORY_SEPARATOR, '/', dirname(__DIR__)).'/',
-    ));
-    $json = rtrim(json_encode(array('repositories' => $package->repositories), $flags), "\n}").','.substr($json, 1);
+    ];
+
+    $json = preg_replace('/\n    "repositories": \[\n.*?\n    \],/s', '', $json);
+    $json = rtrim(json_encode(['repositories' => $package->repositories], $flags), "\n}").','.substr($json, 1);
     file_put_contents('composer.json', $json);
 }
diff --git a/.github/rm-invalid-lowest-lock-files.php b/.github/rm-invalid-lowest-lock-files.php
index c036fd356f..855e69adf9 100644
--- a/.github/rm-invalid-lowest-lock-files.php
+++ b/.github/rm-invalid-lowest-lock-files.php
@@ -11,7 +11,7 @@ $dirs = $_SERVER['argv'];
 
 function getRelevantContent(array $composerJson)
 {
-    $relevantKeys = array(
+    $relevantKeys = [
         'name',
         'require',
         'require-dev',
@@ -22,9 +22,9 @@ function getRelevantContent(array $composerJson)
         'prefer-stable',
         'repositories',
         'extra',
-    );
+    ];
 
-    $relevantContent = array();
+    $relevantContent = [];
 
     foreach (array_intersect($relevantKeys, array_keys($composerJson)) as $key) {
         $relevantContent[$key] = $composerJson[$key];
@@ -44,7 +44,7 @@ function getContentHash(array $composerJson)
     return md5(json_encode($relevantContent));
 }
 
-$composerJsons = array();
+$composerJsons = [];
 
 foreach ($dirs as $dir) {
     if (!file_exists($dir.'/composer.lock') || !$composerLock = @json_decode(file_get_contents($dir.'/composer.lock'), true)) {
@@ -61,11 +61,11 @@ foreach ($dirs as $dir) {
         @unlink($dir.'/composer.lock');
         continue;
     }
-    $composerLock += array('packages' => array(), 'packages-dev' => array());
-    $composerJsons[$composerJson['name']] = array($dir, $composerLock['packages'] + $composerLock['packages-dev'], getRelevantContent($composerJson));
+    $composerLock += ['packages' => [], 'packages-dev' => []];
+    $composerJsons[$composerJson['name']] = [$dir, $composerLock['packages'] + $composerLock['packages-dev'], getRelevantContent($composerJson)];
 }
 
-$referencedCommits = array();
+$referencedCommits = [];
 
 foreach ($composerJsons as list($dir, $lockedPackages)) {
     foreach ($lockedPackages as $lockedJson) {
@@ -85,7 +85,7 @@ foreach ($composerJsons as list($dir, $lockedPackages)) {
             continue;
         }
 
-        foreach (array('minimum-stability', 'prefer-stable') as $key) {
+        foreach (['minimum-stability', 'prefer-stable'] as $key) {
             if (array_key_exists($key, $composerJsons[$name][2])) {
                 $lockedJson[$key] = $composerJsons[$name][2][$key];
             }
@@ -116,10 +116,10 @@ $sh = curl_share_init();
 curl_share_setopt($sh, CURLSHOPT_SHARE, CURL_LOCK_DATA_COOKIE);
 curl_share_setopt($sh, CURLSHOPT_SHARE, CURL_LOCK_DATA_DNS);
 curl_share_setopt($sh, CURLSHOPT_SHARE, CURL_LOCK_DATA_SSL_SESSION);
-$chs = array();
+$chs = [];
 
 foreach ($referencedCommits as $name => $dirsByCommit) {
-    $chs[] = $ch = array(curl_init(), fopen($_SERVER['HOME'].'/.cache/composer/repo/https---repo.packagist.org/provider-'.strtr($name, '/', '$').'.json', 'wb'));
+    $chs[] = $ch = [curl_init(), fopen($_SERVER['HOME'].'/.cache/composer/repo/https---repo.packagist.org/provider-'.strtr($name, '/', '$').'.json', 'wb')];
     curl_setopt($ch[0], CURLOPT_URL, 'https://repo.packagist.org/p/'.$name.'.json');
     curl_setopt($ch[0], CURLOPT_FILE, $ch[1]);
     curl_setopt($ch[0], CURLOPT_SHARE, $sh);
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index aff58f2ef1..bf6eb4b8e4 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -97,7 +97,7 @@ jobs:
             -   name: Install dependencies
                 run: |
                     echo "::group::composer update"
-                    composer update --no-progress --no-suggest --ansi
+                    composer update --no-progress --ansi
                     echo "::endgroup::"
                     echo "::group::install phpunit"
                     ./phpunit install
diff --git a/.travis.yml b/.travis.yml
index 0d7bd87293..f40d27b9d7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -185,7 +185,7 @@ install:
       export SYMFONY_VERSION=$(grep branch-version composer.json | grep -o '[0-9.x]*')
 
       if [[ ! $deps ]]; then
-          php .github/build-packages.php HEAD^ $SYMFONY_VERSION src/Symfony/Bridge/PhpUnit src/Symfony/Contracts
+          php .github/build-packages.php HEAD^ $SYMFONY_VERSION src/Symfony/Bridge/PhpUnit
       else
           export SYMFONY_DEPRECATIONS_HELPER=weak &&
           cp composer.json composer.json.orig &&
@@ -228,7 +228,6 @@ install:
       # Legacy tests are skipped when deps=high and when the current branch version has not the same major version number as the next one
       [[ $deps = high && ${SYMFONY_VERSION%.*} != $(git ls-remote -q --heads | cut -f2 | grep -FA1 /$SYMFONY_VERSION | tail -n 1 | grep -o '[0-9]*' | head -n 1) ]] && export LEGACY=,legacy
 
-      export COMPOSER_ROOT_VERSION=$SYMFONY_VERSION.x-dev
       if [[ $deps ]]; then mv composer.json.phpunit composer.json; fi
 
     - |
@@ -268,7 +267,6 @@ install:
                   SYMFONY_VERSION=$(echo $SYMFONY_VERSION | awk '{print $1 - 1}')
                   echo -e "\\n\\e[33;1mChecking out Symfony $SYMFONY_VERSION and running tests with patched components as deps\\e[0m"
                   export SYMFONY_REQUIRE=">=$SYMFONY_VERSION"
-                  export COMPOSER_ROOT_VERSION=$SYMFONY_VERSION.x-dev
                   git fetch --depth=2 origin $SYMFONY_VERSION
                   git checkout -m FETCH_HEAD
                   COMPONENTS=$(echo "$COMPONENTS" | xargs dirname | xargs -n1 -I{} bash -c "[ -e '{}/phpunit.xml.dist' ] && echo '{}'" | sort)
@@ -287,8 +285,6 @@ install:
           else
               if [[ $PHP = 7.4* ]]; then
                   # add return types before running the test suite
-                  rm src/Symfony/Contracts -Rf && mv vendor/symfony/contracts src/Symfony/Contracts
-                  ln -sd $(realpath src/Symfony/Contracts) vendor/symfony/contracts
                   sed -i 's/"\*\*\/Tests\/"//' composer.json
                   composer install --optimize-autoloader
                   SYMFONY_PATCH_TYPE_DECLARATIONS=force=object php .github/patch-types.php
diff --git a/src/Symfony/Component/Cache/composer.json b/src/Symfony/Component/Cache/composer.json
index 44bcd6c997..6ed94842e7 100644
--- a/src/Symfony/Component/Cache/composer.json
+++ b/src/Symfony/Component/Cache/composer.json
@@ -37,13 +37,13 @@
         "symfony/config": "^4.2|^5.0",
         "symfony/dependency-injection": "^3.4|^4.1|^5.0",
         "symfony/filesystem": "^4.4|^5.0",
-        "symfony/http-kernel": "^4.4|^5.0",
+        "symfony/http-kernel": "^4.4",
         "symfony/var-dumper": "^4.4|^5.0"
     },
     "conflict": {
         "doctrine/dbal": "<2.5",
         "symfony/dependency-injection": "<3.4",
-        "symfony/http-kernel": "<4.4",
+        "symfony/http-kernel": "<4.4|>=5.0",
         "symfony/var-dumper": "<4.4"
     },
     "autoload": {