> ## Documentation Index > Fetch the complete documentation index at: https://docs.agentfront.dev/llms.txt > Use this file to discover all available pages before exploring further. # ChannelRegistry > Registry that manages channel instances, advertises capabilities, and provides lookup methods. ## Overview `ChannelRegistry` extends `RegistryAbstract` and manages all channel instances in a scope. It advertises `experimental: { 'claude/channel': {} }` in server capabilities when channels are registered. ## Methods ### getChannels Get all channel entries. ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} getChannels(): ChannelEntry[] ``` ### getChannelInstances Get all concrete channel instances. ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} getChannelInstances(): ChannelInstance[] ``` ### findByName Find a channel by its declared name. ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} findByName(name: string): ChannelInstance | undefined ``` ### hasAny Check if any channels are registered. ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} hasAny(): boolean ``` ### size Get the number of registered channels. ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} get size(): number ``` ### getCapabilities Get MCP server capabilities contributed by channels. ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} getCapabilities(): Partial ``` Returns `{ experimental: { 'claude/channel': {} } }` when channels exist, empty object otherwise. ### subscribe Subscribe to channel registry changes. ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} subscribe( opts: { immediate?: boolean }, cb: (e: ChannelChangeEvent) => void ): () => void ``` Returns an unsubscribe function. ## ChannelChangeEvent ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} type ChannelChangeEvent = { kind: 'added' | 'updated' | 'removed' | 'reset'; changeScope: 'global' | 'session'; sessionId?: string; version: number; snapshot: readonly ChannelEntry[]; }; ``` ## Accessing the Registry The channel registry is available on the scope after initialization: ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} // From a tool context const scope = this.scope as unknown as { channels?: ChannelRegistry }; const channels = scope.channels; if (channels?.hasAny()) { const allChannels = channels.getChannels(); const chatBridge = channels.findByName('chat-bridge'); } ``` ## Session-Scoped Subscriptions Channel notifications are **session-scoped**. Sessions must be subscribed to a channel to receive its notifications. This prevents data from leaking between connected agents. Subscription methods are on `NotificationService` (accessed via `scope.notifications`): ### subscribeChannel ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} scope.notifications.subscribeChannel(sessionId: string, channelName: string): boolean ``` Subscribe a session to a specific channel. Returns `true` if this is a new subscription. ### unsubscribeChannel ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} scope.notifications.unsubscribeChannel(sessionId: string, channelName: string): boolean ``` Remove a session's subscription to a channel. ### subscribeAllChannels ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} scope.notifications.subscribeAllChannels(sessionId: string, channelNames: string[]): void ``` Bulk subscribe a session to multiple channels. Called automatically during MCP initialize when the client has `claude/channel` capability. ### isChannelSubscribed ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} scope.notifications.isChannelSubscribed(sessionId: string, channelName: string): boolean ``` ### getSubscribersForChannel ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} scope.notifications.getSubscribersForChannel(channelName: string): string[] ``` Returns all session IDs subscribed to a channel. ### getChannelSubscriptions ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} scope.notifications.getChannelSubscriptions(sessionId: string): string[] ``` Returns all channel names a session is subscribed to. **Auto-subscription:** When a session initializes with `experimental: { 'claude/channel': {} }` capability, it is automatically subscribed to all available channels. Channel subscriptions are cleaned up automatically when a session disconnects. ## Session-Targeted Delivery Events from session-scoped sources (agent completion, job completion) carry the originating `sessionId` and are delivered ONLY to that session: ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} // ChannelInstance.pushNotification() with targetSessionId channel.pushNotification('Job completed', { job: 'daily-report' }, targetSessionId); // ^^^^^^^^^^^^^^^^ // only this session receives it ``` Global events (webhooks, file changes, app events) have no `targetSessionId` and go to all subscribed sessions. ## Replay Buffer Channels with `replay: { enabled: true }` buffer events for later delivery: ### replayBufferedEvents ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} channel.replayBufferedEvents(sessionId: string): number ``` Replay all buffered events to a session. Returns the number of events replayed. Replayed events include `replayed: "true"` in their meta. ### clearReplayBuffer ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} channel.clearReplayBuffer(): void ``` Session-targeted events are NOT buffered (they're ephemeral to the session). Only global events are stored in the replay buffer. ## ChannelNotificationService The companion service for sending notifications (session-scoped): ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} const scope = this.scope as unknown as { channelNotifications?: ChannelNotificationService; }; // Send to all sessions subscribed to 'status' channel scope.channelNotifications?.send('status', 'Deployment complete'); // Send to a specific session only scope.channelNotifications?.sendToSession(sessionId, 'Job result', { source: 'jobs' }); ``` ## ChannelEventBus The in-process event bus for `app-event` sources: ```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}} const scope = this.scope as unknown as { channelEventBus?: ChannelEventBus }; // Emit an event that channels with matching app-event source receive scope.channelEventBus?.emit('app:error', { message: 'Connection refused', level: 'critical', }); ``` ## Related * [@Channel Decorator](/frontmcp/sdk-reference/decorators/channel) — decorator configuration * [ChannelContext](/frontmcp/sdk-reference/contexts/channel-context) — context class * [Channels Guide](/frontmcp/servers/channels) — full documentation