diff --git a/src/Client/Http/RequestFactory.php b/src/Client/Http/RequestFactory.php
index a5d6088..8334a10 100644
--- a/src/Client/Http/RequestFactory.php
+++ b/src/Client/Http/RequestFactory.php
@@ -24,7 +24,7 @@
 
 use const PHP_QUERY_RFC3986;
 
-final class RequestFactory
+final readonly class RequestFactory
 {
     private UriInterface|null $uri;
 
diff --git a/src/Client/Http/RequestOptions.php b/src/Client/Http/RequestOptions.php
index 772ffd5..7f04e25 100644
--- a/src/Client/Http/RequestOptions.php
+++ b/src/Client/Http/RequestOptions.php
@@ -4,7 +4,7 @@
 
 namespace SimPod\ClickHouseClient\Client\Http;
 
-final class RequestOptions
+final readonly class RequestOptions
 {
     /** @param array<string, mixed> $params */
     public function __construct(
diff --git a/src/Client/Http/RequestSettings.php b/src/Client/Http/RequestSettings.php
index 0f99893..96d9b15 100644
--- a/src/Client/Http/RequestSettings.php
+++ b/src/Client/Http/RequestSettings.php
@@ -4,7 +4,7 @@
 
 namespace SimPod\ClickHouseClient\Client\Http;
 
-final class RequestSettings
+final readonly class RequestSettings
 {
     /** @var array<string, float|int|string> */
     public array $settings;
diff --git a/src/Client/PsrClickHouseAsyncClient.php b/src/Client/PsrClickHouseAsyncClient.php
index 356c2bc..35ffc5d 100644
--- a/src/Client/PsrClickHouseAsyncClient.php
+++ b/src/Client/PsrClickHouseAsyncClient.php
@@ -21,7 +21,7 @@
 
 use function uniqid;
 
-class PsrClickHouseAsyncClient implements ClickHouseAsyncClient
+readonly class PsrClickHouseAsyncClient implements ClickHouseAsyncClient
 {
     private SqlFactory $sqlFactory;
 
diff --git a/src/Client/PsrClickHouseClient.php b/src/Client/PsrClickHouseClient.php
index b5bb102..8eb08b9 100644
--- a/src/Client/PsrClickHouseClient.php
+++ b/src/Client/PsrClickHouseClient.php
@@ -36,7 +36,7 @@
 use function sprintf;
 use function uniqid;
 
-class PsrClickHouseClient implements ClickHouseClient
+readonly class PsrClickHouseClient implements ClickHouseClient
 {
     private ValueFormatter $valueFormatter;
 
diff --git a/src/Format/Json.php b/src/Format/Json.php
index ebc42ae..f715d20 100644
--- a/src/Format/Json.php
+++ b/src/Format/Json.php
@@ -11,7 +11,7 @@
  * @template T
  * @implements Format<\SimPod\ClickHouseClient\Output\Json<T>>
  */
-final class Json implements Format
+final readonly class Json implements Format
 {
     /** @throws JsonException */
     public static function output(string $contents): Output
diff --git a/src/Format/JsonCompact.php b/src/Format/JsonCompact.php
index 9f986ea..6921ca7 100644
--- a/src/Format/JsonCompact.php
+++ b/src/Format/JsonCompact.php
@@ -11,7 +11,7 @@
  * @template T
  * @implements Format<\SimPod\ClickHouseClient\Output\JsonCompact<T>>
  */
-final class JsonCompact implements Format
+final readonly class JsonCompact implements Format
 {
     /** @throws JsonException */
     public static function output(string $contents): Output
diff --git a/src/Format/JsonEachRow.php b/src/Format/JsonEachRow.php
index 819d35a..2856261 100644
--- a/src/Format/JsonEachRow.php
+++ b/src/Format/JsonEachRow.php
@@ -11,7 +11,7 @@
  * @template T
  * @implements Format<\SimPod\ClickHouseClient\Output\JsonEachRow<T>>
  */
-final class JsonEachRow implements Format
+final readonly class JsonEachRow implements Format
 {
     /** @throws JsonException */
     public static function output(string $contents): Output
diff --git a/src/Format/Null_.php b/src/Format/Null_.php
index 5766ccb..28df85f 100644
--- a/src/Format/Null_.php
+++ b/src/Format/Null_.php
@@ -12,7 +12,7 @@
  * @template T
  * @implements Format<\SimPod\ClickHouseClient\Output\Null_<T>>
  */
-final class Null_ implements Format
+final readonly class Null_ implements Format
 {
     public static function output(string $contents): Output
     {
diff --git a/src/Format/Pretty.php b/src/Format/Pretty.php
index 3978bb0..f94a6eb 100644
--- a/src/Format/Pretty.php
+++ b/src/Format/Pretty.php
@@ -11,7 +11,7 @@
  * @template T
  * @implements Format<Basic<T>>
  */
-final class Pretty implements Format
+final readonly class Pretty implements Format
 {
     public static function output(string $contents): Output
     {
diff --git a/src/Format/PrettySpace.php b/src/Format/PrettySpace.php
index c0da02d..99686de 100644
--- a/src/Format/PrettySpace.php
+++ b/src/Format/PrettySpace.php
@@ -11,7 +11,7 @@
  * @template T
  * @implements Format<Basic<T>>
  */
-final class PrettySpace implements Format
+final readonly class PrettySpace implements Format
 {
     public static function output(string $contents): Output
     {
diff --git a/src/Format/RowBinary.php b/src/Format/RowBinary.php
index ff3eb55..58ca45e 100644
--- a/src/Format/RowBinary.php
+++ b/src/Format/RowBinary.php
@@ -11,7 +11,7 @@
  * @template T
  * @implements Format<Basic<T>>
  */
-final class RowBinary implements Format
+final readonly class RowBinary implements Format
 {
     public static function output(string $contents): Output
     {
diff --git a/src/Format/TabSeparated.php b/src/Format/TabSeparated.php
index 5944855..c67d472 100644
--- a/src/Format/TabSeparated.php
+++ b/src/Format/TabSeparated.php
@@ -11,7 +11,7 @@
  * @template T
  * @implements Format<Basic<T>>
  */
-final class TabSeparated implements Format
+final readonly class TabSeparated implements Format
 {
     public static function output(string $contents): Output
     {
diff --git a/src/Logger/LoggerChain.php b/src/Logger/LoggerChain.php
index 6c97721..b05cf47 100644
--- a/src/Logger/LoggerChain.php
+++ b/src/Logger/LoggerChain.php
@@ -4,7 +4,7 @@
 
 namespace SimPod\ClickHouseClient\Logger;
 
-final class LoggerChain implements SqlLogger
+final readonly class LoggerChain implements SqlLogger
 {
     /** @param SqlLogger[] $loggers */
     public function __construct(private array $loggers = [])
diff --git a/src/Logger/PsrLogger.php b/src/Logger/PsrLogger.php
index e6ad7d7..40bcf6c 100644
--- a/src/Logger/PsrLogger.php
+++ b/src/Logger/PsrLogger.php
@@ -6,7 +6,7 @@
 
 use Psr\Log\LoggerInterface;
 
-final class PsrLogger implements SqlLogger
+final readonly class PsrLogger implements SqlLogger
 {
     public function __construct(private LoggerInterface $logger)
     {
diff --git a/src/Output/Basic.php b/src/Output/Basic.php
index f2a608a..0ecfe05 100644
--- a/src/Output/Basic.php
+++ b/src/Output/Basic.php
@@ -9,7 +9,7 @@
  * @template T
  * @implements Output<T>
  */
-final class Basic implements Output
+final readonly class Basic implements Output
 {
     public function __construct(public string $contents)
     {
diff --git a/src/Output/Json.php b/src/Output/Json.php
index 4a96cab..553f087 100644
--- a/src/Output/Json.php
+++ b/src/Output/Json.php
@@ -15,7 +15,7 @@
  * @template T
  * @implements Output<T>
  */
-final class Json implements Output
+final readonly class Json implements Output
 {
     /** @var list<T> */
     public array $data;
diff --git a/src/Output/JsonCompact.php b/src/Output/JsonCompact.php
index 782f3fe..a844c9b 100644
--- a/src/Output/JsonCompact.php
+++ b/src/Output/JsonCompact.php
@@ -15,7 +15,7 @@
  * @template T
  * @implements Output<T>
  */
-final class JsonCompact implements Output
+final readonly class JsonCompact implements Output
 {
     /** @var list<T> */
     public array $data;
diff --git a/src/Output/JsonEachRow.php b/src/Output/JsonEachRow.php
index a54d146..6be4118 100644
--- a/src/Output/JsonEachRow.php
+++ b/src/Output/JsonEachRow.php
@@ -17,7 +17,7 @@
  * @template T
  * @implements Output<T>
  */
-final class JsonEachRow implements Output
+final readonly class JsonEachRow implements Output
 {
     /** @var list<T> */
     public array $data;
diff --git a/src/Output/Null_.php b/src/Output/Null_.php
index ae4f8b1..6ff92d3 100644
--- a/src/Output/Null_.php
+++ b/src/Output/Null_.php
@@ -11,7 +11,7 @@
  * @template T
  * @implements Output<T>
  */
-final class Null_ implements Output
+final readonly class Null_ implements Output
 {
     public function __construct(string $_)
     {
diff --git a/src/Param/ParamValueConverterRegistry.php b/src/Param/ParamValueConverterRegistry.php
index 286c3df..148ce72 100644
--- a/src/Param/ParamValueConverterRegistry.php
+++ b/src/Param/ParamValueConverterRegistry.php
@@ -32,9 +32,9 @@
  * @phpstan-type Converter Closure(mixed, Type|string|null, bool):(StreamInterface|string)
  * @phpstan-type ConverterRegistry array<string, Converter>
  */
-final class ParamValueConverterRegistry
+final readonly class ParamValueConverterRegistry
 {
-    private const CaseInsensitiveTypes = [
+    private const array CaseInsensitiveTypes = [
         'bool',
         'date',
         'date32',
diff --git a/src/Snippet/CurrentDatabase.php b/src/Snippet/CurrentDatabase.php
index ab7d641..47eed32 100644
--- a/src/Snippet/CurrentDatabase.php
+++ b/src/Snippet/CurrentDatabase.php
@@ -9,7 +9,7 @@
 use SimPod\ClickHouseClient\Exception\ServerError;
 use SimPod\ClickHouseClient\Format\JsonEachRow;
 
-final class CurrentDatabase
+final readonly class CurrentDatabase
 {
     /**
      * @throws ClientExceptionInterface
diff --git a/src/Snippet/DatabaseSize.php b/src/Snippet/DatabaseSize.php
index 0354c00..40cfc62 100644
--- a/src/Snippet/DatabaseSize.php
+++ b/src/Snippet/DatabaseSize.php
@@ -12,7 +12,7 @@
 use SimPod\ClickHouseClient\Format\JsonEachRow;
 use SimPod\ClickHouseClient\Sql\Expression;
 
-final class DatabaseSize
+final readonly class DatabaseSize
 {
     /**
      * @throws ClientExceptionInterface
diff --git a/src/Snippet/Parts.php b/src/Snippet/Parts.php
index 065b631..78a1ce4 100644
--- a/src/Snippet/Parts.php
+++ b/src/Snippet/Parts.php
@@ -13,7 +13,7 @@
 
 use function sprintf;
 
-final class Parts
+final readonly class Parts
 {
     /**
      * @return array<array<string, mixed>>
diff --git a/src/Snippet/ShowCreateTable.php b/src/Snippet/ShowCreateTable.php
index f1bde5a..60891fb 100644
--- a/src/Snippet/ShowCreateTable.php
+++ b/src/Snippet/ShowCreateTable.php
@@ -9,7 +9,7 @@
 use SimPod\ClickHouseClient\Exception\ServerError;
 use SimPod\ClickHouseClient\Format\JsonEachRow;
 
-final class ShowCreateTable
+final readonly class ShowCreateTable
 {
     /**
      * @throws ClientExceptionInterface
diff --git a/src/Snippet/ShowDatabases.php b/src/Snippet/ShowDatabases.php
index 042c680..468d842 100644
--- a/src/Snippet/ShowDatabases.php
+++ b/src/Snippet/ShowDatabases.php
@@ -11,7 +11,7 @@
 
 use function array_map;
 
-final class ShowDatabases
+final readonly class ShowDatabases
 {
     /**
      * @return list<string>
diff --git a/src/Snippet/TableSizes.php b/src/Snippet/TableSizes.php
index 054b0c0..daad74c 100644
--- a/src/Snippet/TableSizes.php
+++ b/src/Snippet/TableSizes.php
@@ -13,7 +13,7 @@
 use SimPod\ClickHouseClient\Sql\Expression;
 
 /** @phpstan-type Entry array{table: string, database: string, size: string, min_date: string, max_date: string} */
-final class TableSizes
+final readonly class TableSizes
 {
     /**
      * @return array<Entry>
diff --git a/src/Snippet/Version.php b/src/Snippet/Version.php
index a78944f..a482d47 100644
--- a/src/Snippet/Version.php
+++ b/src/Snippet/Version.php
@@ -9,7 +9,7 @@
 use SimPod\ClickHouseClient\Exception\ServerError;
 use SimPod\ClickHouseClient\Format\JsonEachRow;
 
-final class Version
+final readonly class Version
 {
     /**
      * @throws ClientExceptionInterface
diff --git a/src/Sql/Escaper.php b/src/Sql/Escaper.php
index 04b2da0..f963cf8 100644
--- a/src/Sql/Escaper.php
+++ b/src/Sql/Escaper.php
@@ -11,7 +11,7 @@
  *
  * @link https://github.com/ClickHouse/clickhouse-jdbc/blob/8481c1323f5de09bb9dbbf67085e5e1b2585756a/src/main/java/ru/yandex/clickhouse/ClickHouseUtil.java
  */
-final class Escaper
+final readonly class Escaper
 {
     public static function escape(string $s): string
     {
diff --git a/src/Sql/Expression.php b/src/Sql/Expression.php
index adb289c..50b86f7 100644
--- a/src/Sql/Expression.php
+++ b/src/Sql/Expression.php
@@ -4,7 +4,7 @@
 
 namespace SimPod\ClickHouseClient\Sql;
 
-final class Expression
+final readonly class Expression
 {
     public string $innerExpression;
 
diff --git a/src/Sql/SqlFactory.php b/src/Sql/SqlFactory.php
index 504915c..6308025 100644
--- a/src/Sql/SqlFactory.php
+++ b/src/Sql/SqlFactory.php
@@ -13,7 +13,7 @@
 use function str_replace;
 
 /** @internal */
-final class SqlFactory
+final readonly class SqlFactory
 {
     public function __construct(private ValueFormatter $valueFormatter)
     {
diff --git a/tests/ClickHouseVersion.php b/tests/ClickHouseVersion.php
index ca85ac7..e1095d4 100644
--- a/tests/ClickHouseVersion.php
+++ b/tests/ClickHouseVersion.php
@@ -15,9 +15,9 @@
 
 use const STR_PAD_LEFT;
 
-final class ClickHouseVersion
+final readonly class ClickHouseVersion
 {
-    private const EnvName = 'CLICKHOUSE_VERSION';
+    private const string EnvName = 'CLICKHOUSE_VERSION';
 
     /** @throws RuntimeException */
     public static function get(): int