diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c812b74e..dcc2fd09 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -41,11 +41,11 @@ jobs:
   build_test:
     strategy:
       matrix:
-        drupal-version: [ 9, 8 ]
+        drupal-version: [ 9, 10 ]
       fail-fast: false
     runs-on: ubuntu-latest
     container:
-      image: quay.io/pantheon-public/build-tools-ci:8.x-php7.4
+      image: quay.io/pantheon-public/build-tools-ci:8.x-php8.1
       options: --user root
     name: Build and test (Drupal ${{ matrix.drupal-version }})
     env:
diff --git a/README.md b/README.md
index a87cced4..54dd00dd 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# Search API Pantheon version 8.0 (for solr 8 & Drupal 8/9)
+# Search API Pantheon version 8.0 (for solr 8 & Drupal 9/10)
 
 [![Search API Pantheon](https://github.com/pantheon-systems/search_api_pantheon/actions/workflows/ci.yml/badge.svg?branch=8.x)](https://github.com/pantheon-systems/search_api_pantheon/actions/workflows/ci.yml)
 [![Limited Availability](https://img.shields.io/badge/Pantheon-Limited_Availability-yellow?logo=pantheon&color=FFDC28)](https://pantheon.io/docs/oss-support-levels#limited-availability)
@@ -10,7 +10,7 @@
 
 This module is for you if you meet the following requirements:
 
-* Using Drupal 8.8/9.2+
+* Using Drupal 9.4/10
 
 * Hosting the Drupal site on Pantheon's platform
 
@@ -49,7 +49,7 @@ Composer is the way you should be managing your drupal module requirements. This
 
 - [Search API Solr](https://www.drupal.org/project/search_api_solr). Search API Solr makes search API work with Apache Solr. Composer will manage which version.
 
-- [Guzzle](https://docs.guzzlephp.org/en/stable/). Guzzle version 6 is standard with Drupal Core `8.x | 9.x` (read 8.x OR 9.x).
+- [Guzzle](https://docs.guzzlephp.org/en/stable/). Guzzle version 6 is standard with Drupal Core `9.x | 10.x` (read 9.x OR 10.x).
 
 ## Install
 
@@ -233,4 +233,4 @@ with the concept usage in a Solr context:
 
 
 * `drush search-api-pantheon:force-cleanup` (`sapfc`) This command will delete all of the contents for the given
-  Solr server (no matter if hash or index_id have changed).
\ No newline at end of file
+  Solr server (no matter if hash or index_id have changed).
diff --git a/RoboFile.php b/RoboFile.php
index e0cdcc64..f2e8f46a 100644
--- a/RoboFile.php
+++ b/RoboFile.php
@@ -80,11 +80,13 @@ public function testFull(int $drupal_version = 9, string $site_name = NULL) {
     $this->testCreateSite($site_name, $options);
     $this->testConnectionGit($site_name, 'dev', 'git');
     $this->testCloneSite($site_name);
-    $this->testAllowPlugins($site_name);
+    $this->testAllowPlugins($site_name, $drupal_version);
+    $this->testPhpVersion($site_name);
 
-    // If received Drupal 8, downgrade the recently created site to Drupal 8.
-    if ($drupal_version === 8) {
-      $this->testDowngradeToDrupal8($site_name);
+    // If received Drupal 10, upgrade the recently created site to Drupal 10.
+    if ($drupal_version === 10) {
+      // @todo Make it downgrade to Drupal 9 when Drupal 10 becomes the default version.
+      $this->testUpgradeToDrupal10($site_name);
     }
 
     // Composer require the corresponding modules, push to Pantheon and install the site.
@@ -180,7 +182,7 @@ public function testCreateSite(string $site_name, array $options = ['org' => NUL
     if (empty($site_info)) {
       $home = $_SERVER['HOME'];
       $toReturn = $this->taskExec(static::$TERMINUS_EXE)
-        ->args('site:create', $site_name, $site_name, 'drupal9');
+        ->args('site:create', $site_name, $site_name, 'drupal-composer-managed');
       if ( !empty( $options['org'] ) ) {
         $toReturn->option('org', $options['org']);
       }
@@ -308,26 +310,101 @@ public function testCloneSite(string $site_name) {
    *
    * @param string $site_name
    *   The machine name of the site to add the allow plugins section to.
+   * @param int $drupal_version
+   *   The major version of Drupal to use.
    */
-  public function testAllowPlugins(string $site_name) {
-    $site_folder = $this->getSiteFolder($site_name);
-    chdir($site_folder);
+  public function testAllowPlugins(string $site_name, int $drupal_version) {
     $plugins = [
-      'composer/installers',
-      'drupal/core-composer-scaffold',
-      'cweagans/composer-patches',
+      'drupal/core-project-message',
     ];
+    if ($drupal_version === 10) {
+      $plugins[] = 'phpstan/extension-installer';
+      // @todo Remove once all of the modules have been correctly upgraded.
+      $plugins[] = 'mglaman/composer-drupal-lenient';
+    }
+    if (count($plugins)) {
+      $site_folder = $this->getSiteFolder($site_name);
+      chdir($site_folder);
+
+      foreach ($plugins as $plugin_name) {
+        $this->taskExec('composer')
+          ->args(
+            'config',
+            '--no-interaction',
+            'allow-plugins.' . $plugin_name,
+            'true'
+          )
+          ->run();
+      }
+    }
+  }
+
+  /**
+   * Upgrade given site to Drupal 10.
+   *
+   * @param string $site_name
+   *   The machine name of the site to downgrade.
+   */
+  public function testUpgradeToDrupal10(string $site_name) {
+    $site_folder = $this->getSiteFolder($site_name);
+    chdir($site_folder);
+
+    // Remove composer lock.
+    $this->taskExec('rm')
+      ->args('composer.lock')
+      ->run();
+
+    $this->taskExec('composer')
+      ->args(
+        'config',
+        'minimum-stability',
+        'dev'
+      )
+      ->run();
+
+    $this->taskExec('composer')
+      ->args(
+        'config',
+        'platform.php',
+        '8.1'
+      )
+      ->run();
+
+    $this->taskExec('composer')
+      ->args(
+        'require',
+        '--no-update',
+        'drupal/core-recommended:^10',
+        'drupal/core-project-message:^10',
+        'drupal/core-composer-scaffold:^10',
+        'pantheon-systems/drupal-integrations:^10',
+        'mglaman/composer-drupal-lenient'
+      )
+      ->run();
+
+    $this->taskExec('composer')
+      ->args(
+        'require',
+        '--no-update',
+        '--dev',
+        'drupal/core-dev:^10'
+      )
+      ->run();
 
-    foreach ($plugins as $plugin_name) {
-      $this->taskExec('composer')
+    $this->taskExec('composer')
+      ->args('update')
+      ->run();
+
+    $this->taskExec('composer')
         ->args(
           'config',
-          '--no-interaction',
-          'allow-plugins.' . $plugin_name,
-          'true'
+          '--merge',
+          '--json',
+          'extra.drupal-lenient.allowed-list',
+          '["drupal/search_api_pantheon"]'
         )
         ->run();
-    }
+    return ResultData::EXITCODE_OK;
   }
 
   /**
@@ -373,11 +450,18 @@ public function testDowngradeToDrupal8(string $site_name) {
   public function testRequireSolr(string $site_name, string $constraint = '^8') {
     $site_folder = $this->getSiteFolder($site_name);
     chdir($site_folder);
+    // Always test again latest version of search_api_solr.
     $this->taskExec('composer')
       ->args(
-              'require',
-              'pantheon-systems/search_api_pantheon ' . $constraint,
-          )
+        'require',
+        'drupal/search_api_solr:dev-4.x',
+      )
+      ->run();
+    $this->taskExec('composer')
+      ->args(
+        'require',
+        'pantheon-systems/search_api_pantheon ' . $constraint,
+      )
       ->run();
     return ResultData::EXITCODE_OK;
   }
@@ -648,6 +732,21 @@ protected function siteInfo(string $site_name) {
     return NULL;
   }
 
+  /**
+   * Set correct PHP version for the given site.
+   *
+   * @param string $site_name
+   *   The machine name of the site to set the Solr version for.
+   */
+  public function testPhpVersion(string $site_name) {
+    $site_folder = $this->getSiteFolder($site_name);
+    $pantheon_yml_contents = Yaml::parseFile($site_folder . '/pantheon.yml');
+    $pantheon_yml_contents['php_version'] = 8.1;
+    $pantheon_yml_contents = Yaml::dump($pantheon_yml_contents);
+    file_put_contents($site_folder . '/pantheon.yml', $pantheon_yml_contents);
+    $this->output->writeln($pantheon_yml_contents);
+  }
+
   /**
    * Set correct Solr version for the given site.
    *
@@ -679,7 +778,7 @@ public function testSolrIndexCreate(string $site_name, string $env = 'dev') {
           '--',
           'cim',
           '--partial',
-          '--source=modules/composer/search_api_pantheon/.ci/config',
+          '--source=modules/contrib/search_api_pantheon/.ci/config',
           '-y'
         )
         ->run();
diff --git a/composer.json b/composer.json
index 33391e19..c2ee5268 100644
--- a/composer.json
+++ b/composer.json
@@ -42,12 +42,11 @@
         "ext-json": "*",
         "ext-zip": "*",
         "drupal/search_api_solr": "^4.2",
-        "guzzlehttp/guzzle": "^6.5.2",
+        "guzzlehttp/guzzle": "^6.5.2|^7.4",
         "http-interop/http-factory-guzzle": "^1.0",
         "kint-php/kint": "^4.1",
-        "php-http/guzzle6-adapter": "^2.0",
         "psr/event-dispatcher": "^1.0",
-        "symfony/finder": "^4|^5"
+        "symfony/finder": "^4.4|^5|^6"
     },
     "require-dev": {
         "consolidation/robo": "^3.0",
diff --git a/modules/search_api_pantheon_admin/search_api_pantheon_admin.info.yml b/modules/search_api_pantheon_admin/search_api_pantheon_admin.info.yml
index ed8b21b6..55910169 100644
--- a/modules/search_api_pantheon_admin/search_api_pantheon_admin.info.yml
+++ b/modules/search_api_pantheon_admin/search_api_pantheon_admin.info.yml
@@ -1,7 +1,7 @@
 name: Search API Pantheon Admin
 type: module
 description: Administer a Pantheon Search server
-core_version_requirement: ^8.8 || ^9
+core_version_requirement: ^9.4 || ^10
 package: Search
 dependencies:
   - search_api_solr:search_api_solr
diff --git a/modules/search_api_pantheon_examples/search_api_pantheon_examples.info.yml b/modules/search_api_pantheon_examples/search_api_pantheon_examples.info.yml
index 6103488f..dbf6b77e 100644
--- a/modules/search_api_pantheon_examples/search_api_pantheon_examples.info.yml
+++ b/modules/search_api_pantheon_examples/search_api_pantheon_examples.info.yml
@@ -1,7 +1,7 @@
 name: Search API Pantheon Examples
 type: module
 description: Contains some examples of things you could do with Search API Pantheon module. This module should not be enabled in prod.
-core_version_requirement: ^8.8 || ^9
+core_version_requirement: ^9.4 || ^10
 package: Search
 dependencies:
   - search_api_pantheon:search_api_pantheon
diff --git a/search_api_pantheon.info.yml b/search_api_pantheon.info.yml
index 650d0c9d..46e2f95a 100644
--- a/search_api_pantheon.info.yml
+++ b/search_api_pantheon.info.yml
@@ -1,7 +1,7 @@
 name: Search API Pantheon
 type: module
 description: Search API + Solr + Pantheon integration
-core_version_requirement: ^8.8 || ^9
+core_version_requirement: ^9.4 || ^10
 package: Search
 dependencies:
   - search_api_solr:search_api_solr
diff --git a/src/Plugin/SolrConnector/PantheonSolrConnector.php b/src/Plugin/SolrConnector/PantheonSolrConnector.php
index 2f87711e..05bd5882 100644
--- a/src/Plugin/SolrConnector/PantheonSolrConnector.php
+++ b/src/Plugin/SolrConnector/PantheonSolrConnector.php
@@ -8,8 +8,6 @@
 use Drupal\search_api_solr\SolrConnector\SolrConnectorPluginBase;
 use Drupal\search_api_solr\SolrConnectorInterface;
 use Drupal\search_api_pantheon\Services\Endpoint as PantheonEndpoint;
-use Psr\Log\LoggerAwareInterface;
-use Psr\Log\LoggerAwareTrait;
 use Solarium\Client as SolariumClient;
 use Solarium\Core\Client\Endpoint;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -31,9 +29,7 @@
 class PantheonSolrConnector extends SolrConnectorPluginBase implements
     SolrConnectorInterface,
     PluginFormInterface,
-    ContainerFactoryPluginInterface,
-    LoggerAwareInterface {
-  use LoggerAwareTrait;
+    ContainerFactoryPluginInterface {
 
   /**
    * @var object|null
diff --git a/src/Solarium/EventDispatcher/EventProxy.php b/src/Solarium/EventDispatcher/EventProxy.php
index 1a76e1bc..dd6543a4 100644
--- a/src/Solarium/EventDispatcher/EventProxy.php
+++ b/src/Solarium/EventDispatcher/EventProxy.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\search_api_pantheon\Solarium\EventDispatcher;
 
-use Symfony\Component\EventDispatcher\Event;
+use Symfony\Contracts\EventDispatcher\Event;
 
 /**
  * A proxy for events defined by symfony contracts to be used with older Drupal.
diff --git a/src/Solarium/EventDispatcher/Psr14Bridge.php b/src/Solarium/EventDispatcher/Psr14Bridge.php
index 572012d3..bf797de2 100644
--- a/src/Solarium/EventDispatcher/Psr14Bridge.php
+++ b/src/Solarium/EventDispatcher/Psr14Bridge.php
@@ -4,7 +4,7 @@
 
 use Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher;
 use Psr\EventDispatcher\EventDispatcherInterface;
-use Symfony\Component\EventDispatcher\Event;
+use Symfony\Contracts\EventDispatcher\Event;
 
 /**
  * A helper to decorate the legacy EventDispatcherInterface::dispatch().