diff --git a/src/swoole/Swoole/Async/Client.php b/src/swoole/Swoole/Async/Client.php
new file mode 100644
index 0000000..7b5eeee
--- /dev/null
+++ b/src/swoole/Swoole/Async/Client.php
@@ -0,0 +1,83 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Swoole\Async;
+
+/**
+ * @since 6.0.0-rc1
+ */
+class Client extends \Swoole\Client
+{
+    public const MSG_OOB = 1;
+
+    public const MSG_PEEK = 2;
+
+    public const MSG_DONTWAIT = 64;
+
+    public const MSG_WAITALL = 256;
+
+    public const SHUT_RDWR = 2;
+
+    public const SHUT_RD = 0;
+
+    public const SHUT_WR = 1;
+
+    private $onConnect;
+
+    private $onError;
+
+    private $onReceive;
+
+    private $onClose;
+
+    private $onBufferFull;
+
+    private $onBufferEmpty;
+
+    private $onSSLReady;
+
+    public function __construct(int $type)
+    {
+    }
+
+    public function __destruct()
+    {
+    }
+
+    public function connect(string $host, int $port = 0, float $timeout = 0.5, int $sock_flag = 0): bool
+    {
+    }
+
+    public function sleep(): bool
+    {
+    }
+
+    public function wakeup(): bool
+    {
+    }
+
+    public function pause(): bool
+    {
+    }
+
+    public function resume(): bool
+    {
+    }
+
+    public function enableSSL(?callable $onSslReady = null): bool
+    {
+    }
+
+    public function isConnected(): bool
+    {
+    }
+
+    public function close(bool $force = false): bool
+    {
+    }
+
+    public function on(string $host, callable $callback): bool
+    {
+    }
+}
diff --git a/src/swoole/Swoole/Client.php b/src/swoole/Swoole/Client.php
index 9a321d8..1635370 100644
--- a/src/swoole/Swoole/Client.php
+++ b/src/swoole/Swoole/Client.php
@@ -117,6 +117,8 @@ public function shutdown(int $how): bool
     /**
      * This method is available only when OpenSSL support is enabled (i.e., when Swoole is installed with configuration
      * option "--enable-openssl" included).
+     *
+     * @return bool TRUE if SSL handshake is successful; otherwise FALSE.
      */
     public function enableSSL(): bool
     {
diff --git a/src/swoole/Swoole/Coroutine.php b/src/swoole/Swoole/Coroutine.php
index f9546cb..873cbe7 100644
--- a/src/swoole/Swoole/Coroutine.php
+++ b/src/swoole/Swoole/Coroutine.php
@@ -477,11 +477,17 @@ public static function waitPid(int $pid, float $timeout = -1): array|false
     }
 
     /**
+     * Wait for given signal(s) with a timeout.
+     *
+     * @param int|array<int> $signals An integer or an array of integers representing the signal number(s).
+     *                                Before Swoole v6.0.0-rc1, only integer is supported.
+     * @param float $timeout The timeout value in seconds. Minimum value is 0.001. -1 means no timeout.
+     * @return bool Returns true on success. Returns false on failure.
      * @alias Alias of method \Swoole\Coroutine\System::waitSignal().
      * @see \Swoole\Coroutine\System::waitSignal()
      * @since 4.5.0
      */
-    public static function waitSignal(int $signo, float $timeout = -1): bool
+    public static function waitSignal(int|array $signals, float $timeout = -1): bool
     {
     }
 
diff --git a/src/swoole/Swoole/Coroutine/Http/Server.php b/src/swoole/Swoole/Coroutine/Http/Server.php
index 4c89013..778e7f6 100644
--- a/src/swoole/Swoole/Coroutine/Http/Server.php
+++ b/src/swoole/Swoole/Coroutine/Http/Server.php
@@ -36,7 +36,15 @@ public function set(array $settings): bool
     {
     }
 
-    public function handle(string $pattern, callable $callback): void
+    /**
+     * Register a callback function to handle the HTTP request specified by the URL pattern.
+     *
+     * @param string $pattern The URL pattern to match, e.g., "/index".
+     * @param callable $callback The callback function to handle the HTTP request.
+     * @return bool Return true on success. Return false on failure.
+     *              Before Swoole v6.0.0-rc1, it returns void.
+     */
+    public function handle(string $pattern, callable $callback): bool
     {
     }
 
diff --git a/src/swoole/Swoole/Coroutine/System.php b/src/swoole/Swoole/Coroutine/System.php
index 91cfe6b..e75172b 100644
--- a/src/swoole/Swoole/Coroutine/System.php
+++ b/src/swoole/Swoole/Coroutine/System.php
@@ -102,11 +102,17 @@ public static function waitPid(int $pid, float $timeout = -1): array|false
     }
 
     /**
+     * Wait for given signal(s) with a timeout.
+     *
+     * @param int|array<int> $signals An integer or an array of integers representing the signal number(s).
+     *                                Before Swoole v6.0.0-rc1, only integer is supported.
+     * @param float $timeout The timeout value in seconds. Minimum value is 0.001. -1 means no timeout.
+     * @return bool Returns true on success. Returns false on failure.
      * @alias This method has an alias of \Swoole\Coroutine::waitSignal().
      * @see \Swoole\Coroutine::waitSignal()
      * @since 4.5.0
      */
-    public static function waitSignal(int $signo, float $timeout = -1): bool
+    public static function waitSignal(int|array $signals, float $timeout = -1): bool
     {
     }
 
diff --git a/src/swoole/constants.php b/src/swoole/constants.php
index 983620c..fb40467 100644
--- a/src/swoole/constants.php
+++ b/src/swoole/constants.php
@@ -5,12 +5,12 @@
 /*
  * Swoole version information.
  */
-define('SWOOLE_VERSION', '6.0.0-dev');
+define('SWOOLE_VERSION', '6.0.0-RC1');
 define('SWOOLE_VERSION_ID', 60000);
 define('SWOOLE_MAJOR_VERSION', 6);
 define('SWOOLE_MINOR_VERSION', 0);
 define('SWOOLE_RELEASE_VERSION', 0);
-define('SWOOLE_EXTRA_VERSION', 'dev');
+define('SWOOLE_EXTRA_VERSION', '');
 
 /*
  * If debug logging is enabled or not in Swoole.
@@ -304,6 +304,7 @@
 #ifdef HAVE_SPINLOCK
 define('SWOOLE_SPINLOCK', 5); # Supported only if the Spin Locks option is provided in the POSIX thread (pthread) libraries.
 #endif
+define('SWOOLE_COROLOCK', 6); # @since v6.0.0-rc1
 
 /*
  * Following SIG_* and PRIO_* constants are set only when PHP extension pcntl (to support Process Control) is not
@@ -564,6 +565,8 @@
  */
 define('SOCKET_ECANCELED', 125);
 
+define('TCP_INFO', 11); // @since v6.0.0-rc1
+
 /*
  * Constants in this section are used in Swoole servers.
  */
diff --git a/src/swoole/functions.php b/src/swoole/functions.php
index c8b694d..8a6047a 100644
--- a/src/swoole/functions.php
+++ b/src/swoole/functions.php
@@ -102,7 +102,7 @@ function swoole_test_kernel_coroutine(int $count = 100, float $sleep_time = 1.0)
  * @alias This function has an alias function swoole_select().
  * @see swoole_select()
  */
-function swoole_client_select(array &$read_array, array &$write_array, array &$error_array, float $timeout = 0.5): int|false
+function swoole_client_select(array &$read, array &$write, array &$except, float $timeout = 0.5): int|false
 {
 }
 
@@ -110,7 +110,7 @@ function swoole_client_select(array &$read_array, array &$write_array, array &$e
  * @alias This function is an alias of function swoole_client_select().
  * @see swoole_client_select()
  */
-function swoole_select(array &$read_array, array &$write_array, array &$error_array, float $timeout = 0.5): int|false
+function swoole_select(array &$read, array &$write, array &$except, float $timeout = 0.5): int|false
 {
 }