diff --git a/.github/workflows/rector-cs.yml b/.github/workflows/rector-cs.yml
new file mode 100644
index 0000000..e79b80c
--- /dev/null
+++ b/.github/workflows/rector-cs.yml
@@ -0,0 +1,27 @@
+name: Rector & CS fix
+
+on:
+  pull_request:
+    paths:
+      - 'config/**'
+      - 'src/**'
+      - 'tests/**'
+      - 'rector.php'
+      - '.php-cs-fixer.dist.php'
+      - 'composer.json'
+      - '.github/workflows/rector-cs.yml'
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  rector-cs:
+    permissions:
+      contents: write  # Required to commit formatting fixes back to the PR
+    uses: yiisoft/actions/.github/workflows/rector-cs.yml@master
+    with:
+      php: '8.0'
diff --git a/.github/workflows/rector.yml b/.github/workflows/rector.yml
deleted file mode 100644
index 11a3e74..0000000
--- a/.github/workflows/rector.yml
+++ /dev/null
@@ -1,26 +0,0 @@
-on:
-  pull_request:
-    paths-ignore:
-      - 'docs/**'
-      - 'README.md'
-      - 'CHANGELOG.md'
-      - '.gitignore'
-      - '.gitattributes'
-      - 'infection.json.dist'
-      - 'psalm.xml'
-
-name: rector
-
-permissions:
-  contents: read
-
-jobs:
-  rector:
-    permissions:
-      contents: write # Required to commit automated Rector and CS fixes.
-    uses: yiisoft/actions/.github/workflows/rector.yml@master
-    with:
-      os: >-
-        ['ubuntu-latest']
-      php: >-
-        ['8.4']
diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
new file mode 100644
index 0000000..9851c4e
--- /dev/null
+++ b/.php-cs-fixer.dist.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+use PhpCsFixer\Finder;
+use PhpCsFixer\Runner\Parallel\ParallelConfigFactory;
+use Yiisoft\CodeStyle\ConfigBuilder;
+
+$finder = (new Finder())->in([
+    __DIR__ . '/src',
+    __DIR__ . '/tests',
+    __DIR__ . '/config',
+]);
+
+return ConfigBuilder::build()
+    ->setCacheFile(__DIR__ . '/runtime/.php-cs-fixer.cache')
+    ->setRiskyAllowed(true)
+    ->setParallelConfig(ParallelConfigFactory::detect())
+    ->setRules([
+        '@Yiisoft/Core' => true,
+        '@Yiisoft/Core:risky' => true,
+    ])
+    ->setFinder($finder);
diff --git a/.styleci.yml b/.styleci.yml
deleted file mode 100644
index 1ab379b..0000000
--- a/.styleci.yml
+++ /dev/null
@@ -1,85 +0,0 @@
-preset: psr12
-risky: true
-
-version: 8.1
-
-finder:
-  exclude:
-    - docs
-    - vendor
-
-enabled:
-  - alpha_ordered_traits
-  - array_indentation
-  - array_push
-  - combine_consecutive_issets
-  - combine_consecutive_unsets
-  - combine_nested_dirname
-  - declare_strict_types
-  - dir_constant
-  - fully_qualified_strict_types
-  - function_to_constant
-  - hash_to_slash_comment
-  - is_null
-  - logical_operators
-  - magic_constant_casing
-  - magic_method_casing
-  - method_separation
-  - modernize_types_casting
-  - native_function_casing
-  - native_function_type_declaration_casing
-  - no_alias_functions
-  - no_empty_comment
-  - no_empty_phpdoc
-  - no_empty_statement
-  - no_extra_block_blank_lines
-  - no_short_bool_cast
-  - no_superfluous_elseif
-  - no_unneeded_control_parentheses
-  - no_unneeded_curly_braces
-  - no_unneeded_final_method
-  - no_unset_cast
-  - no_unused_imports
-  - no_unused_lambda_imports
-  - no_useless_else
-  - no_useless_return
-  - normalize_index_brace
-  - php_unit_dedicate_assert
-  - php_unit_dedicate_assert_internal_type
-  - php_unit_expectation
-  - php_unit_mock
-  - php_unit_mock_short_will_return
-  - php_unit_namespaced
-  - php_unit_no_expectation_annotation
-  - phpdoc_no_empty_return
-  - phpdoc_no_useless_inheritdoc
-  - phpdoc_order
-  - phpdoc_property
-  - phpdoc_scalar
-  - phpdoc_singular_inheritdoc
-  - phpdoc_trim
-  - phpdoc_trim_consecutive_blank_line_separation
-  - phpdoc_type_to_var
-  - phpdoc_types
-  - phpdoc_types_order
-  - print_to_echo
-  - regular_callable_call
-  - return_assignment
-  - self_accessor
-  - self_static_accessor
-  - set_type_to_cast
-  - short_array_syntax
-  - short_list_syntax
-  - simplified_if_return
-  - single_quote
-  - standardize_not_equals
-  - ternary_to_null_coalescing
-  - trailing_comma_in_multiline_array
-  - unalign_double_arrow
-  - unalign_equals
-  - empty_loop_body_braces
-  - integer_literal_case
-  - union_type_without_spaces
-
-disabled:
-  - function_declaration
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 772bcfa..f04b5bf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,7 @@
 
 ## 3.0.2 under development
 
-- no changes in this release.
+- Chg #81: Add explicit use imports for classes and constants (@vjik)
 
 ## 3.0.1 December 17, 2025
 
diff --git a/composer.json b/composer.json
index a1b22fd..41f3173 100644
--- a/composer.json
+++ b/composer.json
@@ -37,13 +37,15 @@
         "yiisoft/cookies": "^1.0"
     },
     "require-dev": {
-        "maglnet/composer-require-checker": "^4.4",
+        "bamarni/composer-bin-plugin": "*",
+        "friendsofphp/php-cs-fixer": "^3.95",
         "nyholm/psr7": "^1.8.2",
         "phpunit/phpunit": "^9.6.22",
         "rector/rector": "^2.0.10",
         "roave/infection-static-analysis-plugin": "^1.25",
         "spatie/phpunit-watcher": "^1.23.6",
         "vimeo/psalm": "^4.30 || ^5.6 || ^6.8.8",
+        "yiisoft/code-style": "^1.0",
         "yiisoft/di": "^1.2.1"
     },
     "suggest": {
@@ -60,6 +62,11 @@
         }
     },
     "extra": {
+        "bamarni-bin": {
+            "bin-links": true,
+            "target-directory": "tools",
+            "forward-command": true
+        },
         "config-plugin-options": {
             "source-directory": "config"
         },
@@ -72,10 +79,13 @@
         "sort-packages": true,
         "allow-plugins": {
             "infection/extension-installer": true,
-            "composer/package-versions-deprecated": true
+            "composer/package-versions-deprecated": true,
+            "bamarni/composer-bin-plugin": true
         }
     },
     "scripts": {
+        "cs-fix": "php-cs-fixer fix",
+        "rector": "rector",
         "test": "phpunit --testdox --no-interaction",
         "test-watch": "phpunit-watcher watch"
     }
diff --git a/rector.php b/rector.php
index 63713ce..f6a4dcd 100644
--- a/rector.php
+++ b/rector.php
@@ -4,19 +4,18 @@
 
 use Rector\CodeQuality\Rector\Class_\InlineConstructorDefaultToPropertyRector;
 use Rector\Config\RectorConfig;
-use Rector\Set\ValueObject\LevelSetList;
+use Rector\Php74\Rector\Closure\ClosureToArrowFunctionRector;
 
-return static function (RectorConfig $rectorConfig): void {
-    $rectorConfig->paths([
+return RectorConfig::configure()
+    ->withPaths([
         __DIR__ . '/src',
         __DIR__ . '/tests',
+        __DIR__ . '/config',
+    ])
+    ->withPhpSets(php80: true)
+    ->withRules([
+        InlineConstructorDefaultToPropertyRector::class,
+    ])
+    ->withSkip([
+        ClosureToArrowFunctionRector::class,
     ]);
-
-    // register a single rule
-    $rectorConfig->rule(InlineConstructorDefaultToPropertyRector::class);
-
-    // define sets of rules
-    $rectorConfig->sets([
-        LevelSetList::UP_TO_PHP_80,
-    ]);
-};
diff --git a/runtime/.gitignore b/runtime/.gitignore
new file mode 100644
index 0000000..d6b7ef3
--- /dev/null
+++ b/runtime/.gitignore
@@ -0,0 +1,2 @@
+*
+!.gitignore
diff --git a/src/Flash/Flash.php b/src/Flash/Flash.php
index 207df27..e7682eb 100644
--- a/src/Flash/Flash.php
+++ b/src/Flash/Flash.php
@@ -20,9 +20,7 @@ final class Flash implements FlashInterface
 
     private ?string $sessionId = null;
 
-    public function __construct(private SessionInterface $session)
-    {
-    }
+    public function __construct(private SessionInterface $session) {}
 
     public function get(string $key)
     {
diff --git a/src/NullSession.php b/src/NullSession.php
index 7602e34..9faf51c 100644
--- a/src/NullSession.php
+++ b/src/NullSession.php
@@ -14,39 +14,27 @@ public function get(string $key, $default = null)
         return null;
     }
 
-    public function set(string $key, $value): void
-    {
-    }
+    public function set(string $key, $value): void {}
 
-    public function close(): void
-    {
-    }
+    public function close(): void {}
 
-    public function open(): void
-    {
-    }
+    public function open(): void {}
 
     public function isActive(): bool
     {
         return false;
     }
 
-    public function regenerateId(): void
-    {
-    }
+    public function regenerateId(): void {}
 
-    public function discard(): void
-    {
-    }
+    public function discard(): void {}
 
     public function all(): array
     {
         return [];
     }
 
-    public function remove(string $key): void
-    {
-    }
+    public function remove(string $key): void {}
 
     public function has(string $key): bool
     {
@@ -58,9 +46,7 @@ public function pull(string $key, $default = null)
         return null;
     }
 
-    public function destroy(): void
-    {
-    }
+    public function destroy(): void {}
 
     public function getCookieParameters(): array
     {
@@ -72,16 +58,12 @@ public function getId(): ?string
         return null;
     }
 
-    public function setId(string $sessionId): void
-    {
-    }
+    public function setId(string $sessionId): void {}
 
     public function getName(): string
     {
         return 'null';
     }
 
-    public function clear(): void
-    {
-    }
+    public function clear(): void {}
 }
diff --git a/src/Session.php b/src/Session.php
index 5b3ca4b..a83fede 100644
--- a/src/Session.php
+++ b/src/Session.php
@@ -7,6 +7,8 @@
 use SessionHandlerInterface;
 use Throwable;
 
+use const PHP_SESSION_ACTIVE;
+
 /**
  * Session provides session data management and the related configurations.
  *
@@ -99,7 +101,7 @@ public function open(): void
              */
             $this->sessionId = session_id();
         } catch (Throwable $e) {
-            throw new SessionException('Failed to start session.', (int)$e->getCode(), $e);
+            throw new SessionException('Failed to start session.', (int) $e->getCode(), $e);
         }
     }
 
@@ -124,7 +126,7 @@ public function regenerateId(): void
                     $this->sessionId = session_id();
                 }
             } catch (Throwable $e) {
-                throw new SessionException('Failed to regenerate ID.', (int)$e->getCode(), $e);
+                throw new SessionException('Failed to regenerate ID.', (int) $e->getCode(), $e);
             }
         }
     }
diff --git a/src/SessionException.php b/src/SessionException.php
index 344ea05..6c37b8b 100644
--- a/src/SessionException.php
+++ b/src/SessionException.php
@@ -6,6 +6,4 @@
 
 use RuntimeException;
 
-final class SessionException extends RuntimeException
-{
-}
+final class SessionException extends RuntimeException {}
diff --git a/src/SessionMiddleware.php b/src/SessionMiddleware.php
index 73a060d..7e337bf 100644
--- a/src/SessionMiddleware.php
+++ b/src/SessionMiddleware.php
@@ -11,6 +11,7 @@
 use Psr\Http\Server\RequestHandlerInterface;
 use Throwable;
 use Yiisoft\Cookies\Cookie;
+use Exception;
 
 /**
  * Session middleware handles storing session ID into a response cookie and
@@ -18,9 +19,7 @@
  */
 final class SessionMiddleware implements MiddlewareInterface
 {
-    public function __construct(private SessionInterface $session)
-    {
-    }
+    public function __construct(private SessionInterface $session) {}
 
     public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
     {
@@ -42,7 +41,7 @@ public function process(ServerRequestInterface $request, RequestHandlerInterface
     /**
      * Close session and add/modify response session cookie if necessary.
      *
-     * @throws \Exception
+     * @throws Exception
      */
     private function commitSession(ServerRequestInterface $request, ResponseInterface $response): ResponseInterface
     {
@@ -83,8 +82,8 @@ private function commitSession(ServerRequestInterface $request, ResponseInterfac
                 ->getUri()
                 ->getScheme() !== 'https') {
             throw new SessionException(
-                '"cookie_secure" is on but connection is not secure. ' .
-                'Either set Session "cookie_secure" option to "0" or make connection secure.'
+                '"cookie_secure" is on but connection is not secure. '
+                . 'Either set Session "cookie_secure" option to "0" or make connection secure.',
             );
         }
 
diff --git a/tests/BadSessionHandler.php b/tests/BadSessionHandler.php
index 1d8c695..e650361 100644
--- a/tests/BadSessionHandler.php
+++ b/tests/BadSessionHandler.php
@@ -4,11 +4,14 @@
 
 namespace Yiisoft\Session\Tests;
 
-final class BadSessionHandler implements \SessionHandlerInterface
+use ReturnTypeWillChange;
+use SessionHandlerInterface;
+
+use function in_array;
+
+final class BadSessionHandler implements SessionHandlerInterface
 {
-    public function __construct(private array $failAt = [])
-    {
-    }
+    public function __construct(private array $failAt = []) {}
 
     public function close(): bool
     {
@@ -20,7 +23,7 @@ public function destroy($session_id): bool
         return $this->getReturnValue('destroy');
     }
 
-    #[\ReturnTypeWillChange]
+    #[ReturnTypeWillChange]
     public function gc($maxlifetime)
     {
         return $this->getReturnValue('gc');
@@ -31,7 +34,7 @@ public function open($save_path, $name): bool
         return $this->getReturnValue('open');
     }
 
-    #[\ReturnTypeWillChange]
+    #[ReturnTypeWillChange]
     public function read($session_id)
     {
         return '';
diff --git a/tests/ConfigTest.php b/tests/ConfigTest.php
index 0f50d3b..a8c6137 100644
--- a/tests/ConfigTest.php
+++ b/tests/ConfigTest.php
@@ -12,6 +12,8 @@
 use Yiisoft\Session\Session;
 use Yiisoft\Session\SessionInterface;
 
+use function dirname;
+
 final class ConfigTest extends TestCase
 {
     public function testBase(): void
@@ -29,8 +31,8 @@ private function createContainer(?array $params = null): Container
     {
         return new Container(
             ContainerConfig::create()->withDefinitions(
-                $this->getDiConfig($params)
-            )
+                $this->getDiConfig($params),
+            ),
         );
     }
 
diff --git a/tests/Flash/FlashTest.php b/tests/Flash/FlashTest.php
index 7177a79..1f2c751 100644
--- a/tests/Flash/FlashTest.php
+++ b/tests/Flash/FlashTest.php
@@ -15,11 +15,6 @@ final class FlashTest extends TestCase
      */
     private SessionInterface $session;
 
-    private function getSession(array $contents = []): SessionInterface
-    {
-        return new MockArraySessionStorage($contents);
-    }
-
     protected function setUp(): void
     {
         parent::setUp();
@@ -235,4 +230,9 @@ public function testGetAll(): void
             'error' => 'Some error message to show',
         ], $flashes);
     }
+
+    private function getSession(array $contents = []): SessionInterface
+    {
+        return new MockArraySessionStorage($contents);
+    }
 }
diff --git a/tests/Flash/MockArraySessionStorage.php b/tests/Flash/MockArraySessionStorage.php
index 08b19eb..bb7ce70 100644
--- a/tests/Flash/MockArraySessionStorage.php
+++ b/tests/Flash/MockArraySessionStorage.php
@@ -16,9 +16,7 @@ final class MockArraySessionStorage implements SessionInterface
 
     private bool $closed = false;
 
-    public function __construct(private array $data = [])
-    {
-    }
+    public function __construct(private array $data = []) {}
 
     public function get(string $key, $default = null)
     {
diff --git a/tests/SessionMiddlewareTest.php b/tests/SessionMiddlewareTest.php
index 1125fba..7de1eba 100644
--- a/tests/SessionMiddlewareTest.php
+++ b/tests/SessionMiddlewareTest.php
@@ -137,7 +137,7 @@ private function setUpRequestHandlerMock(ResponseInterface $response): void
     private function setUpSessionMock(
         bool $cookieDomainProvided = true,
         bool $isActive = true,
-        ?string $sessionId = self::CURRENT_SID
+        ?string $sessionId = self::CURRENT_SID,
     ): void {
         $this->sessionMock
             ->expects($this->any())
diff --git a/tests/SessionTest.php b/tests/SessionTest.php
index 0186abc..3d38dbd 100644
--- a/tests/SessionTest.php
+++ b/tests/SessionTest.php
@@ -9,6 +9,8 @@
 use Yiisoft\Session\Session;
 use Yiisoft\Session\SessionException;
 
+use const PHP_SESSION_NONE;
+
 /**
  * @runTestsInSeparateProcesses
  */
@@ -16,6 +18,14 @@ final class SessionTest extends TestCase
 {
     private ?Session $session = null;
 
+    protected function tearDown(): void
+    {
+        if ($this->session !== null) {
+            $this->session->destroy();
+            $this->session = null;
+        }
+    }
+
     public function getSession(array $options = [], ?SessionHandlerInterface $handler = null): Session
     {
         if ($this->session === null) {
@@ -25,14 +35,6 @@ public function getSession(array $options = [], ?SessionHandlerInterface $handle
         return $this->session;
     }
 
-    protected function tearDown(): void
-    {
-        if ($this->session !== null) {
-            $this->session->destroy();
-            $this->session = null;
-        }
-    }
-
     public function testGetAndSet(): void
     {
         $session = $this->getSession();
diff --git a/tests/SpySessionHandler.php b/tests/SpySessionHandler.php
index 3de12f5..3e63c96 100644
--- a/tests/SpySessionHandler.php
+++ b/tests/SpySessionHandler.php
@@ -4,9 +4,12 @@
 
 namespace Yiisoft\Session\Tests;
 
+use ReturnTypeWillChange;
+use SessionHandlerInterface;
+
 use function array_key_exists;
 
-final class SpySessionHandler implements \SessionHandlerInterface
+final class SpySessionHandler implements SessionHandlerInterface
 {
     private array $calls = [];
 
@@ -27,7 +30,7 @@ public function destroy($session_id): bool
         return true;
     }
 
-    #[\ReturnTypeWillChange]
+    #[ReturnTypeWillChange]
     public function gc($maxlifetime)
     {
         $this->record('gc');
@@ -40,7 +43,7 @@ public function open($save_path, $name): bool
         return true;
     }
 
-    #[\ReturnTypeWillChange]
+    #[ReturnTypeWillChange]
     public function read($session_id)
     {
         $this->record('read');
diff --git a/tools/.gitignore b/tools/.gitignore
new file mode 100644
index 0000000..cf452dc
--- /dev/null
+++ b/tools/.gitignore
@@ -0,0 +1,2 @@
+/*/vendor
+/*/composer.lock
diff --git a/tools/composer-require-checker/composer.json b/tools/composer-require-checker/composer.json
new file mode 100644
index 0000000..498425c
--- /dev/null
+++ b/tools/composer-require-checker/composer.json
@@ -0,0 +1,5 @@
+{
+    "require-dev": {
+        "maglnet/composer-require-checker": "^4.4"
+    }
+}