diff --git a/.gitignore b/.gitignore
index 0a162d7..bd4ef2a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,4 +2,5 @@
 /.idea
 composer.lock
 .phpunit.result.cache
+.twitch_token.json
 tmi.php
diff --git a/composer.json b/composer.json
index 5b1bef4..a4f8e14 100644
--- a/composer.json
+++ b/composer.json
@@ -22,6 +22,8 @@
   "require": {
     "php": "^7.4|^8.0",
     "react/socket": "^1.6",
+    "react/http": "^1.6",
+    "ratchet/pawl": "^0.4",
     "ext-mbstring": "*",
     "ext-json": "*"
   },
diff --git a/src/CommandContext.php b/src/CommandContext.php
new file mode 100644
index 0000000..b20bdb1
--- /dev/null
+++ b/src/CommandContext.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace GhostZero\Tmi;
+
+use GhostZero\Tmi\Events\EventSub\ChatMessageEvent;
+
+class CommandContext
+{
+    public ChatMessageEvent $event;
+    public string $command;
+
+    /**
+     * Arguments after the command name, split by spaces.
+     * @var string[]
+     */
+    public array $args;
+
+    private EventSubClient $client;
+
+    public function __construct(ChatMessageEvent $event, string $command, array $args, EventSubClient $client)
+    {
+        $this->event = $event;
+        $this->command = $command;
+        $this->args = $args;
+        $this->client = $client;
+    }
+
+    /**
+     * Sends a Twitch reply thread to the triggering message.
+     */
+    public function reply(string $message): void
+    {
+        $this->client->sendMessage($this->event->broadcasterUserId, $message, $this->event->messageId);
+    }
+
+    /**
+     * Sends a regular chat message (no reply thread).
+     */
+    public function say(string $message): void
+    {
+        $this->client->sendMessage($this->event->broadcasterUserId, $message);
+    }
+}
diff --git a/src/EventSubClient.php b/src/EventSubClient.php
new file mode 100644
index 0000000..4a195df
--- /dev/null
+++ b/src/EventSubClient.php
@@ -0,0 +1,240 @@
+<?php
+
+namespace GhostZero\Tmi;
+
+use GhostZero\Tmi\Events\EventHandler;
+use GhostZero\Tmi\Events\EventSub\ChatMessageEvent;
+use GhostZero\Tmi\Events\EventSub\ChatNotificationEvent;
+use Ratchet\Client\WebSocket;
+use Ratchet\RFC6455\Messaging\MessageInterface;
+use React\EventLoop\LoopInterface;
+use React\Http\Browser;
+
+class EventSubClient
+{
+    private const WEBSOCKET_URL = 'wss://eventsub.wss.twitch.tv/ws';
+    private const API_SUBSCRIPTIONS_URL = 'https://api.twitch.tv/helix/eventsub/subscriptions';
+    private const API_CHAT_MESSAGES_URL = 'https://api.twitch.tv/helix/chat/messages';
+
+    private EventSubOptions $options;
+    private LoopInterface $loop;
+    private EventHandler $eventHandler;
+    private Browser $browser;
+    private array $commands = [];
+
+    public function __construct(EventSubOptions $options)
+    {
+        $this->options = $options;
+        $this->loop = \React\EventLoop\Factory::create();
+        $this->eventHandler = new EventHandler();
+        $this->browser = new Browser($this->loop);
+    }
+
+    public function connect(): void
+    {
+        $this->connectWebSocket(self::WEBSOCKET_URL);
+        $this->loop->run();
+    }
+
+    public function on(string $event, callable $closure): self
+    {
+        $this->eventHandler->addHandler($event, $closure);
+        return $this;
+    }
+
+    public function any(callable $closure): self
+    {
+        return $this->on('*', $closure);
+    }
+
+    /**
+     * Registers a chat command handler. The command name must include the prefix (e.g. '!hello').
+     * The handler receives a CommandContext with reply() and say() helpers.
+     */
+    public function command(string $name, callable $handler): self
+    {
+        $this->commands[strtolower($name)] = $handler;
+        return $this;
+    }
+
+    /**
+     * Sends a chat message via the Helix API. Pass a replyToMessageId to create a Twitch reply thread.
+     */
+    public function sendMessage(string $broadcasterUserId, string $message, ?string $replyToMessageId = null): void
+    {
+        $body = [
+            'broadcaster_id' => $broadcasterUserId,
+            'sender_id' => $this->options->getBotUserId(),
+            'message' => $message,
+        ];
+
+        if ($replyToMessageId !== null) {
+            $body['reply_parent_message_id'] = $replyToMessageId;
+        }
+
+        $this->browser->post(self::API_CHAT_MESSAGES_URL, [
+            'Authorization' => 'Bearer ' . $this->options->getAccessToken(),
+            'Client-Id' => $this->options->getClientId(),
+            'Content-Type' => 'application/json',
+        ], json_encode($body))->then(
+            function (\Psr\Http\Message\ResponseInterface $response) {
+                $this->debug("Chat message sent: HTTP {$response->getStatusCode()}");
+            },
+            function (\Exception $e) {
+                $this->debug("Failed to send chat message: " . $e->getMessage());
+            }
+        );
+    }
+
+    public function getLoop(): LoopInterface
+    {
+        return $this->loop;
+    }
+
+    public function getEventHandler(): EventHandler
+    {
+        return $this->eventHandler;
+    }
+
+    private function connectWebSocket(string $url): void
+    {
+        \Ratchet\Client\connect($url, [], [], $this->loop)->then(
+            function (WebSocket $conn) {
+                $this->debug("Connected to EventSub WebSocket.");
+
+                $conn->on('message', function (MessageInterface $msg) {
+                    $payload = json_decode((string) $msg, true);
+                    if ($payload !== null) {
+                        $this->handleMessage($payload);
+                    }
+                });
+
+                $conn->on('close', function (int $code, string $reason) {
+                    $this->debug("WebSocket closed: {$code} {$reason}");
+                    if ($this->options->shouldReconnect()) {
+                        $delay = $this->options->getReconnectDelay();
+                        $this->loop->addTimer($delay, fn () => $this->connectWebSocket(self::WEBSOCKET_URL));
+                    }
+                });
+
+                $conn->on('error', function (\Exception $e) {
+                    $this->debug("WebSocket error: " . $e->getMessage());
+                });
+            },
+            function (\Exception $e) {
+                $this->debug("Failed to connect: " . $e->getMessage());
+                if ($this->options->shouldReconnect()) {
+                    $delay = $this->options->getReconnectDelay();
+                    $this->loop->addTimer($delay, fn () => $this->connectWebSocket(self::WEBSOCKET_URL));
+                }
+            }
+        );
+    }
+
+    private function handleMessage(array $payload): void
+    {
+        $this->debug(json_encode($payload));
+
+        $messageType = $payload['metadata']['message_type'] ?? null;
+
+        switch ($messageType) {
+            case 'session_welcome':
+                $sessionId = $payload['payload']['session']['id'];
+                $this->subscribeToEvents($sessionId);
+                break;
+
+            case 'notification':
+                $this->handleNotification($payload['payload']);
+                break;
+
+            case 'session_reconnect':
+                $reconnectUrl = $payload['payload']['session']['reconnect_url'];
+                $this->debug("Reconnecting to: {$reconnectUrl}");
+                $this->connectWebSocket($reconnectUrl);
+                break;
+
+            case 'revocation':
+                $type = $payload['payload']['subscription']['type'] ?? 'unknown';
+                $status = $payload['payload']['subscription']['status'] ?? 'unknown';
+                $this->debug("Subscription revoked — type: {$type}, status: {$status}");
+                break;
+
+            case 'session_keepalive':
+                break;
+        }
+    }
+
+    private function subscribeToEvents(string $sessionId): void
+    {
+        foreach ($this->options->getSubscriptions() as $subscription) {
+            $body = json_encode([
+                'type' => $subscription['type'],
+                'version' => $subscription['version'] ?? '1',
+                'condition' => $subscription['condition'],
+                'transport' => [
+                    'method' => 'websocket',
+                    'session_id' => $sessionId,
+                ],
+            ]);
+
+            $this->browser->post(self::API_SUBSCRIPTIONS_URL, [
+                'Authorization' => 'Bearer ' . $this->options->getAccessToken(),
+                'Client-Id' => $this->options->getClientId(),
+                'Content-Type' => 'application/json',
+            ], $body)->then(
+                function (\Psr\Http\Message\ResponseInterface $response) use ($subscription) {
+                    $this->debug("Subscribed to {$subscription['type']}: HTTP {$response->getStatusCode()}");
+                },
+                function (\Exception $e) use ($subscription) {
+                    $this->debug("Failed to subscribe to {$subscription['type']}: " . $e->getMessage());
+                }
+            );
+        }
+    }
+
+    private function handleNotification(array $payload): void
+    {
+        $subscriptionType = $payload['subscription']['type'] ?? null;
+        $eventData = $payload['event'] ?? [];
+
+        $event = match ($subscriptionType) {
+            'channel.chat.message' => new ChatMessageEvent($eventData),
+            'channel.chat.notification' => new ChatNotificationEvent($eventData),
+            default => null,
+        };
+
+        if ($event !== null) {
+            $this->eventHandler->invoke($event);
+
+            if ($event instanceof ChatMessageEvent) {
+                $this->parseCommand($event);
+            }
+        }
+    }
+
+    private function parseCommand(ChatMessageEvent $event): void
+    {
+        $text = trim($event->messageText);
+
+        if ($text === '' || $text[0] !== '!') {
+            return;
+        }
+
+        $parts = explode(' ', $text, 2);
+        $name = strtolower($parts[0]);
+        $args = isset($parts[1]) ? explode(' ', trim($parts[1])) : [];
+
+        if (!isset($this->commands[$name])) {
+            return;
+        }
+
+        ($this->commands[$name])(new CommandContext($event, $name, $args, $this));
+    }
+
+    private function debug(string $message): void
+    {
+        if ($this->options->isDebug()) {
+            print $message . PHP_EOL;
+        }
+    }
+}
diff --git a/src/EventSubOptions.php b/src/EventSubOptions.php
new file mode 100644
index 0000000..8a79db5
--- /dev/null
+++ b/src/EventSubOptions.php
@@ -0,0 +1,73 @@
+<?php
+
+namespace GhostZero\Tmi;
+
+class EventSubOptions
+{
+    private array $options;
+
+    public function __construct(array $options)
+    {
+        $this->options = $options;
+    }
+
+    public function getAccessToken(): string
+    {
+        return ltrim($this->options['access_token'], 'oauth:');
+    }
+
+    public function getClientId(): string
+    {
+        return $this->options['client_id'];
+    }
+
+    /**
+     * Returns the list of EventSub subscriptions to register.
+     *
+     * Each entry must have:
+     *   - type:      e.g. 'channel.chat.message'
+     *   - version:   (optional, defaults to '1')
+     *   - condition: associative array of condition fields
+     *
+     * Example:
+     *   ['type' => 'channel.chat.message', 'condition' => ['broadcaster_user_id' => '123', 'user_id' => '456']]
+     */
+    public function getSubscriptions(): array
+    {
+        return $this->options['subscriptions'] ?? [];
+    }
+
+    /**
+     * Returns the bot's Twitch user ID used as the sender when posting chat messages.
+     * Reads from the top-level 'user_id' option, falling back to the first subscription's condition.
+     */
+    public function getBotUserId(): string
+    {
+        if (isset($this->options['user_id'])) {
+            return $this->options['user_id'];
+        }
+
+        foreach ($this->options['subscriptions'] ?? [] as $sub) {
+            if (isset($sub['condition']['user_id'])) {
+                return $sub['condition']['user_id'];
+            }
+        }
+
+        throw new \RuntimeException('Bot user ID not configured. Add "user_id" to EventSubOptions or include it in a subscription condition.');
+    }
+
+    public function isDebug(): bool
+    {
+        return $this->options['options']['debug'] ?? false;
+    }
+
+    public function shouldReconnect(): bool
+    {
+        return $this->options['connection']['reconnect'] ?? true;
+    }
+
+    public function getReconnectDelay(): int
+    {
+        return $this->options['connection']['reconnect_delay'] ?? 3;
+    }
+}
diff --git a/src/Events/EventSub/ChatMessageEvent.php b/src/Events/EventSub/ChatMessageEvent.php
new file mode 100644
index 0000000..938d2cc
--- /dev/null
+++ b/src/Events/EventSub/ChatMessageEvent.php
@@ -0,0 +1,51 @@
+<?php
+
+namespace GhostZero\Tmi\Events\EventSub;
+
+use GhostZero\Tmi\Events\Event;
+
+class ChatMessageEvent extends Event
+{
+    public string $broadcasterUserId;
+    public string $broadcasterUserLogin;
+    public string $broadcasterUserName;
+    public string $chatterUserId;
+    public string $chatterUserLogin;
+    public string $chatterUserName;
+    public string $messageId;
+    public string $messageText;
+    public string $messageType;
+    public string $color;
+    public array $badges;
+    public array $fragments;
+    public ?array $cheer;
+    public ?array $reply;
+    public ?string $channelPointsCustomRewardId;
+    public ?string $sourceBroadcasterUserId;
+    public ?string $sourceBroadcasterUserLogin;
+    public ?string $sourceBroadcasterUserName;
+    public bool $isSourceOnly;
+
+    public function __construct(array $event)
+    {
+        $this->broadcasterUserId = $event['broadcaster_user_id'];
+        $this->broadcasterUserLogin = $event['broadcaster_user_login'];
+        $this->broadcasterUserName = $event['broadcaster_user_name'];
+        $this->chatterUserId = $event['chatter_user_id'];
+        $this->chatterUserLogin = $event['chatter_user_login'];
+        $this->chatterUserName = $event['chatter_user_name'];
+        $this->messageId = $event['message_id'];
+        $this->messageText = $event['message']['text'];
+        $this->fragments = $event['message']['fragments'] ?? [];
+        $this->messageType = $event['message_type'];
+        $this->color = $event['color'] ?? '';
+        $this->badges = $event['badges'] ?? [];
+        $this->cheer = $event['cheer'] ?? null;
+        $this->reply = $event['reply'] ?? null;
+        $this->channelPointsCustomRewardId = $event['channel_points_custom_reward_id'] ?? null;
+        $this->sourceBroadcasterUserId = $event['source_broadcaster_user_id'] ?? null;
+        $this->sourceBroadcasterUserLogin = $event['source_broadcaster_user_login'] ?? null;
+        $this->sourceBroadcasterUserName = $event['source_broadcaster_user_name'] ?? null;
+        $this->isSourceOnly = $event['is_source_only'] ?? false;
+    }
+}
diff --git a/src/Events/EventSub/ChatNotificationEvent.php b/src/Events/EventSub/ChatNotificationEvent.php
new file mode 100644
index 0000000..fe94d2c
--- /dev/null
+++ b/src/Events/EventSub/ChatNotificationEvent.php
@@ -0,0 +1,58 @@
+<?php
+
+namespace GhostZero\Tmi\Events\EventSub;
+
+use GhostZero\Tmi\Events\Event;
+
+class ChatNotificationEvent extends Event
+{
+    public string $broadcasterUserId;
+    public string $broadcasterUserLogin;
+    public string $broadcasterUserName;
+    public string $chatterUserId;
+    public string $chatterUserLogin;
+    public string $chatterUserName;
+    public bool $chatterIsAnonymous;
+    public string $color;
+    public array $badges;
+    public string $systemMessage;
+    public string $messageId;
+    public string $messageText;
+    public array $fragments;
+
+    /**
+     * One of: sub, resub, sub_gift, community_sub_gift, gift_paid_upgrade,
+     * prime_paid_upgrade, pay_it_forward, raid, unraid, announcement,
+     * bits_badge_tier, charity_donation, shared_chat_sub, etc.
+     */
+    public string $noticeType;
+
+    /**
+     * Raw event payload for notice-type-specific fields (sub, resub, raid, etc.)
+     */
+    public array $payload;
+
+    public function __construct(array $event)
+    {
+        $this->broadcasterUserId = $event['broadcaster_user_id'];
+        $this->broadcasterUserLogin = $event['broadcaster_user_login'];
+        $this->broadcasterUserName = $event['broadcaster_user_name'];
+        $this->chatterUserId = $event['chatter_user_id'];
+        $this->chatterUserLogin = $event['chatter_user_login'];
+        $this->chatterUserName = $event['chatter_user_name'];
+        $this->chatterIsAnonymous = $event['chatter_is_anonymous'] ?? false;
+        $this->color = $event['color'] ?? '';
+        $this->badges = $event['badges'] ?? [];
+        $this->systemMessage = $event['system_message'] ?? '';
+        $this->messageId = $event['message_id'];
+        $this->messageText = $event['message']['text'] ?? '';
+        $this->fragments = $event['message']['fragments'] ?? [];
+        $this->noticeType = $event['notice_type'];
+        $this->payload = $event;
+    }
+
+    public function getNoticeData(): ?array
+    {
+        return $this->payload[$this->noticeType] ?? null;
+    }
+}
diff --git a/src/OAuthHelper.php b/src/OAuthHelper.php
new file mode 100644
index 0000000..3967452
--- /dev/null
+++ b/src/OAuthHelper.php
@@ -0,0 +1,289 @@
+<?php
+
+namespace GhostZero\Tmi;
+
+use React\Http\HttpServer;
+use React\Http\Browser;
+use React\Http\Message\Response;
+use React\Socket\Server as SocketServer;
+use React\EventLoop\Factory;
+use React\EventLoop\LoopInterface;
+use Psr\Http\Message\ServerRequestInterface;
+
+class OAuthHelper
+{
+    private const AUTH_URL = 'https://id.twitch.tv/oauth2/authorize';
+    private const TOKEN_URL = 'https://id.twitch.tv/oauth2/token';
+    private const VALIDATE_URL = 'https://id.twitch.tv/oauth2/validate';
+
+    private string $clientId;
+    private string $clientSecret;
+    private int $port;
+    private string $tokenFile;
+
+    public function __construct(
+        string $clientId,
+        string $clientSecret,
+        int $port = 3000,
+        string $tokenFile = '.twitch_token.json'
+    ) {
+        $this->clientId = $clientId;
+        $this->clientSecret = $clientSecret;
+        $this->port = $port;
+        $this->tokenFile = $tokenFile;
+    }
+
+    /**
+     * Returns a valid access token, running the OAuth flow when needed.
+     *
+     * @param string[] $scopes Required OAuth scopes.
+     */
+    public function getAccessToken(array $scopes = ['user:read:chat']): string
+    {
+        $token = $this->loadToken();
+
+        if ($token !== null && $this->scopesChanged($token, $scopes)) {
+            $token = null;
+        }
+
+        if ($token !== null && !$this->isTokenExpired($token)) {
+            return $token['access_token'];
+        }
+
+        if ($token !== null && isset($token['refresh_token'])) {
+            try {
+                $refreshed = $this->exchangeToken([
+                    'grant_type' => 'refresh_token',
+                    'refresh_token' => $token['refresh_token'],
+                    'client_id' => $this->clientId,
+                    'client_secret' => $this->clientSecret,
+                ]);
+                $this->saveToken($refreshed);
+                return $refreshed['access_token'];
+            } catch (\Exception $e) {
+                // Fall through to full flow
+            }
+        }
+
+        $token = $this->runOAuthFlow($scopes);
+        $this->saveToken($token);
+        return $token['access_token'];
+    }
+
+    /**
+     * Returns the Twitch user ID for the authenticated account, or null if not yet authorized.
+     */
+    public function getUserId(): ?string
+    {
+        return $this->loadToken()['user_id'] ?? null;
+    }
+
+    /**
+     * Returns the Twitch login name for the authenticated account, or null if not yet authorized.
+     */
+    public function getLogin(): ?string
+    {
+        return $this->loadToken()['login'] ?? null;
+    }
+
+    private function runOAuthFlow(array $scopes): array
+    {
+        $loop = Factory::create();
+        $state = bin2hex(random_bytes(16));
+        $redirectUri = "http://localhost:{$this->port}/callback";
+
+        $authUrl = self::AUTH_URL . '?' . http_build_query([
+            'client_id' => $this->clientId,
+            'redirect_uri' => $redirectUri,
+            'response_type' => 'code',
+            'scope' => implode(' ', $scopes),
+            'state' => $state,
+            'force_verify' => 'true',
+        ]);
+
+        $browser = new Browser($loop);
+        $socket = new SocketServer("127.0.0.1:{$this->port}", $loop);
+
+        $tokenData = null;
+        $flowError = null;
+
+        $httpServer = new HttpServer(
+            function (ServerRequestInterface $request) use (
+                $state, $redirectUri, $browser, $socket, $loop, &$tokenData, &$flowError
+            ) {
+                parse_str($request->getUri()->getQuery(), $params);
+
+                if (($params['state'] ?? '') !== $state) {
+                    return new Response(400, ['Content-Type' => 'text/plain'], 'Invalid state parameter.');
+                }
+
+                if (isset($params['error'])) {
+                    $flowError = $params['error_description'] ?? $params['error'];
+                    $socket->close();
+                    $loop->stop();
+                    return new Response(400, ['Content-Type' => 'text/plain'], "Authorization denied: {$flowError}");
+                }
+
+                $browser->post(self::TOKEN_URL, [
+                    'Content-Type' => 'application/x-www-form-urlencoded',
+                ], http_build_query([
+                    'client_id' => $this->clientId,
+                    'client_secret' => $this->clientSecret,
+                    'code' => $params['code'],
+                    'grant_type' => 'authorization_code',
+                    'redirect_uri' => $redirectUri,
+                ]))->then(
+                    function ($response) use ($browser, $socket, $loop, &$tokenData, &$flowError) {
+                        $data = json_decode((string) $response->getBody(), true);
+
+                        if (!isset($data['access_token'])) {
+                            $flowError = 'Token exchange failed: ' . (string) $response->getBody();
+                            $socket->close();
+                            $loop->stop();
+                            return;
+                        }
+
+                        // Fetch user info so caller knows broadcaster_user_id / user_id
+                        $browser->get(self::VALIDATE_URL, [
+                            'Authorization' => 'OAuth ' . $data['access_token'],
+                        ])->then(
+                            function ($vResponse) use ($data, $socket, $loop, &$tokenData) {
+                                $userInfo = json_decode((string) $vResponse->getBody(), true);
+                                $tokenData = array_merge($data, [
+                                    'expires_at' => time() + ($data['expires_in'] ?? 3600),
+                                    'user_id' => $userInfo['user_id'] ?? null,
+                                    'login' => $userInfo['login'] ?? null,
+                                ]);
+                                $socket->close();
+                                $loop->stop();
+                            },
+                            function () use ($data, $socket, $loop, &$tokenData) {
+                                $tokenData = array_merge($data, [
+                                    'expires_at' => time() + ($data['expires_in'] ?? 3600),
+                                ]);
+                                $socket->close();
+                                $loop->stop();
+                            }
+                        );
+                    },
+                    function (\Exception $e) use ($socket, $loop, &$flowError) {
+                        $flowError = $e->getMessage();
+                        $socket->close();
+                        $loop->stop();
+                    }
+                );
+
+                return new Response(
+                    200,
+                    ['Content-Type' => 'text/html'],
+                    '<!DOCTYPE html><html><body>' .
+                    '<h1>Authorization successful!</h1>' .
+                    '<p>You can close this window and return to the terminal.</p>' .
+                    '</body></html>'
+                );
+            }
+        );
+
+        $httpServer->listen($socket);
+
+        echo PHP_EOL . "Opening Twitch authorization page in your browser..." . PHP_EOL;
+        echo "If it does not open automatically, visit:" . PHP_EOL . PHP_EOL;
+        echo "  {$authUrl}" . PHP_EOL . PHP_EOL;
+        echo "Waiting for authorization on http://localhost:{$this->port}/callback ..." . PHP_EOL;
+
+        $this->openBrowser($authUrl);
+
+        $loop->run();
+
+        if ($flowError !== null) {
+            throw new \RuntimeException("OAuth flow failed: {$flowError}");
+        }
+
+        if (!isset($tokenData['access_token'])) {
+            throw new \RuntimeException('OAuth flow failed: no access token received.');
+        }
+
+        echo "Authorized as: " . ($tokenData['login'] ?? 'unknown') .
+            " (user_id: " . ($tokenData['user_id'] ?? 'unknown') . ")" . PHP_EOL . PHP_EOL;
+
+        return $tokenData;
+    }
+
+    private function exchangeToken(array $params): array
+    {
+        $loop = Factory::create();
+        $browser = new Browser($loop);
+
+        $result = null;
+        $error = null;
+
+        $browser->post(self::TOKEN_URL, [
+            'Content-Type' => 'application/x-www-form-urlencoded',
+        ], http_build_query($params))->then(
+            function ($response) use (&$result, $loop) {
+                $data = json_decode((string) $response->getBody(), true);
+                if (isset($data['access_token'])) {
+                    $data['expires_at'] = time() + ($data['expires_in'] ?? 3600);
+                    $result = $data;
+                }
+                $loop->stop();
+            },
+            function (\Exception $e) use (&$error, $loop) {
+                $error = $e->getMessage();
+                $loop->stop();
+            }
+        );
+
+        $loop->run();
+
+        if ($error !== null || $result === null) {
+            throw new \RuntimeException("Token exchange failed: " . ($error ?? 'empty response'));
+        }
+
+        return $result;
+    }
+
+    private function openBrowser(string $url): void
+    {
+        $escaped = escapeshellarg($url);
+        match (PHP_OS_FAMILY) {
+            'Windows' => exec("start {$escaped}"),
+            'Darwin'  => exec("open {$escaped}"),
+            default   => exec("xdg-open {$escaped} 2>/dev/null &"),
+        };
+    }
+
+    private function loadToken(): ?array
+    {
+        if (!file_exists($this->tokenFile)) {
+            return null;
+        }
+
+        $data = json_decode(file_get_contents($this->tokenFile), true);
+        return is_array($data) ? $data : null;
+    }
+
+    private function saveToken(array $tokenData): void
+    {
+        file_put_contents($this->tokenFile, json_encode($tokenData, JSON_PRETTY_PRINT));
+    }
+
+    private function isTokenExpired(array $tokenData): bool
+    {
+        if (!isset($tokenData['expires_at'])) {
+            return false;
+        }
+        return time() >= ($tokenData['expires_at'] - 60);
+    }
+
+    private function scopesChanged(array $token, array $requestedScopes): bool
+    {
+        $stored = $token['scope'] ?? [];
+        if (is_string($stored)) {
+            $stored = explode(' ', $stored);
+        }
+        sort($stored);
+        sort($requestedScopes);
+        return $stored !== $requestedScopes;
+    }
+}