chore: add channels command

packages/cli/src/ui/AppContainer.tsx

@@ -68,6 +68,7 @@ import {
   flattenMemory,
   type MemoryChangedPayload,
   type ChannelMessagePayload,
+  activeChannels,
   writeToStdout,
   disableMouseEvents,
   enterAlternateScreen,
@@ -1241,6 +1242,22 @@ Logging in with Google... Restarting Gemini CLI to continue.
     };
   }, [channelsEnabled, addMessage]);
 
+  // Warn about requested channels whose MCP servers did not declare capability.
+  const channelWarningFired = useRef(false);
+  useEffect(() => {
+    if (!isMcpReady || !channelsEnabled || channelWarningFired.current) return;
+    channelWarningFired.current = true;
+    const requested = config.getChannels();
+    for (const name of requested) {
+      if (!activeChannels.has(name)) {
+        coreEvents.emitFeedback(
+          'warning',
+          `Channel "${name}" was requested but the MCP server did not declare channel capability.`,
+        );
+      }
+    }
+  }, [isMcpReady, channelsEnabled, config]);
+
   cancelHandlerRef.current = useCallback(
     (shouldRestorePrompt: boolean = true) => {
       const pendingHistoryItems = [

packages/cli/src/ui/commands/channelsCommand.ts

@@ -0,0 +1,39 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { SlashCommand, CommandContext } from './types.js';
+import { CommandKind } from './types.js';
+import {
+  MessageType,
+  type ChannelInfo,
+  type HistoryItemChannelsList,
+} from '../types.js';
+import { activeChannels } from '@google/gemini-cli-core';
+
+export const channelsCommand: SlashCommand = {
+  name: 'channels',
+  description: 'List active message channels from MCP servers',
+  kind: CommandKind.BUILT_IN,
+  autoExecute: true,
+  action: async (context: CommandContext) => {
+    const channels: ChannelInfo[] = Array.from(activeChannels.entries()).map(
+      ([name, capability]) => ({
+        name,
+        displayName: capability.displayName,
+        supportsReply: capability.supportsReply,
+      }),
+    );
+
+    const channelsListItem: HistoryItemChannelsList = {
+      type: MessageType.CHANNELS_LIST,
+      channels,
+    };
+
+    context.ui.addItem(channelsListItem);
+
+    return;
+  },
+};