diff --git a/src/handlers/__tests__/message.test.ts b/src/handlers/__tests__/message.test.ts
index 56606c2..cde03c1 100644
--- a/src/handlers/__tests__/message.test.ts
+++ b/src/handlers/__tests__/message.test.ts
@@ -5,7 +5,6 @@ import { createMessageHandler } from '../message.ts';
 describe('createMessageHandler', () => {
 	const timesAllChannelId = 'C_TIMES_ALL';
 	const workspaceUrl = 'https://workspace.slack.com';
-	const handler = createMessageHandler(timesAllChannelId, workspaceUrl);
 
 	function makeArgs(
 		message: Record<string, unknown>,
@@ -29,6 +28,7 @@ describe('createMessageHandler', () => {
 	}
 
 	it('timesチャンネルのメッセージをtimes-allに転送する', async () => {
+		const handler = createMessageHandler(timesAllChannelId, workspaceUrl);
 		const message = {
 			type: 'message',
 			subtype: undefined,
@@ -53,6 +53,7 @@ describe('createMessageHandler', () => {
 	});
 
 	it('times-以外のチャンネルは転送しない', async () => {
+		const handler = createMessageHandler(timesAllChannelId, workspaceUrl);
 		const message = {
 			type: 'message',
 			subtype: undefined,
@@ -70,6 +71,7 @@ describe('createMessageHandler', () => {
 	});
 
 	it('subtypeを持つメッセージは転送しない', async () => {
+		const handler = createMessageHandler(timesAllChannelId, workspaceUrl);
 		const message = {
 			type: 'message',
 			subtype: 'channel_join',
@@ -86,6 +88,7 @@ describe('createMessageHandler', () => {
 	});
 
 	it('DMメッセージは転送しない', async () => {
+		const handler = createMessageHandler(timesAllChannelId, workspaceUrl);
 		const message = {
 			type: 'message',
 			subtype: undefined,
@@ -102,4 +105,56 @@ describe('createMessageHandler', () => {
 		assert.equal(args.client.conversations.info.mock.callCount(), 0);
 		assert.equal(args.client.chat.postMessage.mock.callCount(), 0);
 	});
+
+	it('同一チャンネルの2回目以降はconversations.infoを呼ばない', async () => {
+		const handler = createMessageHandler(timesAllChannelId, workspaceUrl);
+		const message = {
+			type: 'message',
+			subtype: undefined,
+			channel: 'C_CACHED',
+			channel_type: 'channel',
+			text: 'first',
+			ts: '1234567890.000001',
+			user: 'U12345',
+		};
+		// biome-ignore lint/suspicious/noExplicitAny: テスト用のモック
+		const args1 = makeArgs(message) as any;
+		await handler(args1);
+
+		const message2 = { ...message, text: 'second', ts: '1234567890.000002' };
+		// biome-ignore lint/suspicious/noExplicitAny: テスト用のモック
+		const args2 = makeArgs(message2) as any;
+		await handler(args2);
+
+		assert.equal(args1.client.conversations.info.mock.callCount(), 1);
+		assert.equal(args2.client.conversations.info.mock.callCount(), 0);
+	});
+
+	it('conversations.infoが例外をスローした場合は転送しない', async () => {
+		const handler = createMessageHandler(timesAllChannelId, workspaceUrl);
+		const message = {
+			type: 'message',
+			subtype: undefined,
+			channel: 'C_ERROR',
+			channel_type: 'channel',
+			text: 'hello',
+			ts: '1234567890.123456',
+			user: 'U12345',
+		};
+		const args = {
+			message,
+			client: {
+				conversations: {
+					info: mock.fn(() => Promise.reject(new Error('platform_error'))),
+				},
+				chat: {
+					postMessage: mock.fn(() => Promise.resolve()),
+				},
+			},
+		};
+		// biome-ignore lint/suspicious/noExplicitAny: テスト用のモック
+		await handler(args as any);
+
+		assert.equal(args.client.chat.postMessage.mock.callCount(), 0);
+	});
 });
diff --git a/src/handlers/message.ts b/src/handlers/message.ts
index 7470ce7..2e456fd 100644
--- a/src/handlers/message.ts
+++ b/src/handlers/message.ts
@@ -4,25 +4,75 @@ import { isForwardableMessage } from '../lib/messageFilter.ts';
 import { buildMessageLink } from '../lib/messageLink.ts';
 import { isTimesChannel } from '../lib/timesChannel.ts';
 
+type SlackClient = (AllMiddlewareArgs &
+	SlackEventMiddlewareArgs<'message'>)['client'];
+
+async function getChannelName(
+	client: SlackClient,
+	channelId: string,
+	cache: Map<string, string>,
+): Promise<string | undefined> {
+	const cached = cache.get(channelId);
+	if (cached !== undefined) {
+		return cached;
+	}
+	try {
+		const channelInfo = await client.conversations.info({
+			channel: channelId,
+		});
+		const channelName = channelInfo.channel?.name;
+		if (!channelName) {
+			console.error('channel name not found', {
+				channel: channelId,
+				ok: channelInfo.ok,
+				error: channelInfo.error,
+			});
+			return undefined;
+		}
+		cache.set(channelId, channelName);
+		return channelName;
+	} catch (error) {
+		console.error('conversations.info failed', {
+			channel: channelId,
+			error:
+				error instanceof Error
+					? { name: error.name, message: error.message, stack: error.stack }
+					: error,
+		});
+		return undefined;
+	}
+}
+
 export function createMessageHandler(
 	timesAllChannelId: string,
 	workspaceUrl: string,
 ) {
+	const channelNameCache = new Map<string, string>();
+
 	return async ({
 		message,
 		client,
 	}: AllMiddlewareArgs & SlackEventMiddlewareArgs<'message'>) => {
-		console.log('received message');
+		console.log('received message', {
+			channel: message.channel,
+			subtype: message.subtype,
+			ts: message.ts,
+		});
 		if (!isForwardableMessage(message, timesAllChannelId)) {
+			console.log('skipped: not forwardable', { subtype: message.subtype });
 			return;
 		}
 
-		const channelInfo = await client.conversations.info({
-			channel: message.channel,
-		});
-		const channelName = channelInfo.channel?.name;
-		if (!channelName || !isTimesChannel(channelName)) {
-			console.log(channelName);
+		const channelName = await getChannelName(
+			client,
+			message.channel,
+			channelNameCache,
+		);
+		if (!channelName) {
+			return;
+		}
+		if (!isTimesChannel(channelName)) {
+			console.log('skipped: not a times channel', { channelName });
 			return;
 		}