diff --git a/packages/backend/src/server/api/stream/Connection.ts b/packages/backend/src/server/api/stream/Connection.ts
index 36f7cd93b2..d7340f99fd 100644
--- a/packages/backend/src/server/api/stream/Connection.ts
+++ b/packages/backend/src/server/api/stream/Connection.ts
@@ -52,7 +52,7 @@ export default class Connection {
 	public token?: MiAccessToken;
 	private wsConnection: WebSocket.WebSocket;
 	public subscriber: StreamEventEmitter;
-	private channels: Channel[] = [];
+	private channels: Map<string, Channel> = new Map();
 	private subscribingNotes: Partial<Record<string, number>> = {};
 	public userProfile: MiUserProfile | null = null;
 	public following: Record<string, Pick<MiFollowing, 'withReplies'> | undefined> = {};
@@ -262,7 +262,11 @@ export default class Connection {
 	 */
 	@bindThis
 	public async connectChannel(id: string, params: JsonObject | undefined, channel: string, pong = false) {
-		if (this.channels.length >= MAX_CHANNELS_PER_CONNECTION) {
+		if (this.channels.has(id)) {
+			this.disconnectChannel(id);
+		}
+
+		if (this.channels.size >= MAX_CHANNELS_PER_CONNECTION) {
 			return;
 		}
 
@@ -278,8 +282,12 @@ export default class Connection {
 		}
 
 		// 共有可能チャンネルに接続しようとしていて、かつそのチャンネルに既に接続していたら無意味なので無視
-		if (channelConstructor.shouldShare && this.channels.some(c => c.chName === channel)) {
-			return;
+		if (channelConstructor.shouldShare) {
+			for (const c of this.channels.values()) {
+				if (c.chName === channel) {
+					return;
+				}
+			}
 		}
 
 		const contextId = ContextIdFactory.create();
@@ -289,8 +297,13 @@ export default class Connection {
 		}, contextId);
 		const ch: Channel = await this.moduleRef.create<Channel>(channelConstructor, contextId);
 
-		this.channels.push(ch);
-		ch.init(params ?? {});
+		this.channels.set(ch.id, ch);
+		const valid = await ch.init(params ?? {});
+		if (typeof valid === 'boolean' && !valid) {
+			// 初期化処理の結果、接続拒否されたので切断
+			this.disconnectChannel(id);
+			return;
+		}
 
 		if (pong) {
 			this.sendMessageToWs('connected', {
@@ -332,11 +345,11 @@ export default class Connection {
 	 */
 	@bindThis
 	public disconnectChannel(id: string) {
-		const channel = this.channels.find(c => c.id === id);
+		const channel = this.channels.get(id);
 
 		if (channel) {
 			if (channel.dispose) channel.dispose();
-			this.channels = this.channels.filter(c => c.id !== id);
+			this.channels.delete(id);
 		}
 	}
 
@@ -351,7 +364,7 @@ export default class Connection {
 		if (typeof data.type !== 'string') return;
 		if (typeof data.body === 'undefined') return;
 
-		const channel = this.channels.find(c => c.id === data.id);
+		const channel = this.channels.get(data.id);
 		if (channel != null && channel.onMessage != null) {
 			channel.onMessage(data.type, data.body);
 		}
@@ -363,7 +376,7 @@ export default class Connection {
 	@bindThis
 	public dispose() {
 		if (this.fetchIntervalId) clearInterval(this.fetchIntervalId);
-		for (const c of this.channels.filter(c => c.dispose)) {
+		for (const c of this.channels.values()) {
 			if (c.dispose) c.dispose();
 		}
 	}
diff --git a/packages/backend/src/server/api/stream/channel.ts b/packages/backend/src/server/api/stream/channel.ts
index 21036ee351..010d47a7ff 100644
--- a/packages/backend/src/server/api/stream/channel.ts
+++ b/packages/backend/src/server/api/stream/channel.ts
@@ -8,6 +8,7 @@ import { isInstanceMuted } from '@/misc/is-instance-muted.js';
 import { isUserRelated } from '@/misc/is-user-related.js';
 import { isQuotePacked, isRenotePacked } from '@/misc/is-renote.js';
 import { isChannelRelated } from '@/misc/is-channel-related.js';
+import type { Awaitable } from '@/types.js';
 import type { Packed } from '@/misc/json-schema.js';
 import type { JsonObject, JsonValue } from '@/misc/json-value.js';
 import type Connection from './Connection.js';
@@ -141,7 +142,14 @@ export default abstract class Channel {
 		});
 	}
 
-	public abstract init(params: JsonObject): void;
+	/**
+	 * チャンネルの初期化処理（接続時点での接続可否チェックを兼ねる）
+	 *
+	 * - `void / Promise<void>` を返す場合は、チェックなし
+	 * - `true / Promise<true>` を返す場合は、接続可能
+	 * - `false / Promise<false>` を返す場合は、接続不可（接続を切断）
+	 */
+	public abstract init(params: JsonObject): Awaitable<void | boolean>;
 
 	public dispose?(): void;
 
diff --git a/packages/backend/src/server/api/stream/channels/antenna.ts b/packages/backend/src/server/api/stream/channels/antenna.ts
index a37c2b8fcf..3fb1ad63d4 100644
--- a/packages/backend/src/server/api/stream/channels/antenna.ts
+++ b/packages/backend/src/server/api/stream/channels/antenna.ts
@@ -4,6 +4,8 @@
  */
 
 import { Inject, Injectable, Scope } from '@nestjs/common';
+import { DI } from '@/di-symbols.js';
+import type { AntennasRepository } from '@/models/_.js';
 import { NoteEntityService } from '@/core/entities/NoteEntityService.js';
 import { NoteStreamingHidingService } from '../NoteStreamingHidingService.js';
 import { bindThis } from '@/decorators.js';
@@ -25,6 +27,9 @@ export class AntennaChannel extends Channel {
 		@Inject(REQUEST)
 		request: ChannelRequest,
 
+		@Inject(DI.antennasRepository)
+		private antennasReposiotry: AntennasRepository,
+
 		private noteEntityService: NoteEntityService,
 		private noteStreamingHidingService: NoteStreamingHidingService,
 	) {
@@ -33,12 +38,25 @@ export class AntennaChannel extends Channel {
 	}
 
 	@bindThis
-	public async init(params: JsonObject) {
-		if (typeof params.antennaId !== 'string') return;
+	public async init(params: JsonObject): Promise<boolean> {
+		if (typeof params.antennaId !== 'string') return false;
+		if (!this.user) return false;
+
 		this.antennaId = params.antennaId;
 
+		const antennaExists = await this.antennasReposiotry.exists({
+			where: {
+				id: this.antennaId,
+				userId: this.user.id,
+			},
+		});
+
+		if (!antennaExists) return false;
+
 		// Subscribe stream
 		this.subscriber.on(`antennaStream:${this.antennaId}`, this.onEvent);
+
+		return true;
 	}
 
 	@bindThis
diff --git a/packages/backend/src/server/api/stream/channels/chat-room.ts b/packages/backend/src/server/api/stream/channels/chat-room.ts
index 7f949032e2..f56522716e 100644
--- a/packages/backend/src/server/api/stream/channels/chat-room.ts
+++ b/packages/backend/src/server/api/stream/channels/chat-room.ts
@@ -4,12 +4,14 @@
  */
 
 import { Inject, Injectable, Scope } from '@nestjs/common';
+import { DI } from '@/di-symbols.js';
 import { bindThis } from '@/decorators.js';
 import type { GlobalEvents } from '@/core/GlobalEventService.js';
 import type { JsonObject } from '@/misc/json-value.js';
 import { ChatService } from '@/core/ChatService.js';
 import Channel, { type ChannelRequest } from '../channel.js';
 import { REQUEST } from '@nestjs/core';
+import type { ChatRoomsRepository } from '@/models/_.js';
 
 @Injectable({ scope: Scope.TRANSIENT })
 export class ChatRoomChannel extends Channel {
@@ -23,17 +25,31 @@ export class ChatRoomChannel extends Channel {
 		@Inject(REQUEST)
 		request: ChannelRequest,
 
+		@Inject(DI.chatRoomsRepository)
+		private chatRoomsRepository: ChatRoomsRepository,
+
 		private chatService: ChatService,
 	) {
 		super(request);
 	}
 
 	@bindThis
-	public async init(params: JsonObject) {
-		if (typeof params.roomId !== 'string') return;
+	public async init(params: JsonObject): Promise<boolean> {
+		if (typeof params.roomId !== 'string') return false;
+		if (!this.user) return false;
+
 		this.roomId = params.roomId;
 
+		const room = await this.chatRoomsRepository.findOneBy({
+			id: this.roomId,
+		});
+
+		if (room == null) return false;
+		if (!(await this.chatService.hasPermissionToViewRoomTimeline(this.user.id, room))) return false;
+
 		this.subscriber.on(`chatRoomStream:${this.roomId}`, this.onEvent);
+
+		return true;
 	}
 
 	@bindThis
diff --git a/packages/backend/src/server/api/stream/channels/chat-user.ts b/packages/backend/src/server/api/stream/channels/chat-user.ts
index 36f3f67b28..6d96c658ad 100644
--- a/packages/backend/src/server/api/stream/channels/chat-user.ts
+++ b/packages/backend/src/server/api/stream/channels/chat-user.ts
@@ -29,11 +29,16 @@ export class ChatUserChannel extends Channel {
 	}
 
 	@bindThis
-	public async init(params: JsonObject) {
-		if (typeof params.otherId !== 'string') return;
+	public async init(params: JsonObject): Promise<boolean> {
+		if (typeof params.otherId !== 'string') return false;
+		if (!this.user) return false;
+		if (params.otherId === this.user.id) return false;
+
 		this.otherId = params.otherId;
 
-		this.subscriber.on(`chatUserStream:${this.user!.id}-${this.otherId}`, this.onEvent);
+		this.subscriber.on(`chatUserStream:${this.user.id}-${this.otherId}`, this.onEvent);
+
+		return true;
 	}
 
 	@bindThis
diff --git a/packages/backend/src/server/api/stream/channels/hashtag.ts b/packages/backend/src/server/api/stream/channels/hashtag.ts
index 66a0df3e6b..6ba8963044 100644
--- a/packages/backend/src/server/api/stream/channels/hashtag.ts
+++ b/packages/backend/src/server/api/stream/channels/hashtag.ts
@@ -32,17 +32,19 @@ export class HashtagChannel extends Channel {
 	}
 
 	@bindThis
-	public async init(params: JsonObject) {
-		if (!Array.isArray(params.q)) return;
+	public async init(params: JsonObject): Promise<boolean> {
+		if (!Array.isArray(params.q)) return false;
 		if (!params.q.every((x): x is string[] => (
 			Array.isArray(x) &&
 			x.length >= 1 &&
 			x.every(y => typeof y === 'string')
-		))) return;
+		))) return false;
 		this.q = params.q;
 
 		// Subscribe stream
 		this.subscriber.on('notesStream', this.onNote);
+
+		return true;
 	}
 
 	@bindThis
diff --git a/packages/backend/src/server/api/stream/channels/main.ts b/packages/backend/src/server/api/stream/channels/main.ts
index 68a249cbee..224d9e0d89 100644
--- a/packages/backend/src/server/api/stream/channels/main.ts
+++ b/packages/backend/src/server/api/stream/channels/main.ts
@@ -28,9 +28,10 @@ export class MainChannel extends Channel {
 	}
 
 	@bindThis
-	public async init(params: JsonObject) {
-		// Subscribe main stream channel
-		this.subscriber.on(`mainStream:${this.user!.id}`, async data => {
+	public async init(params: JsonObject): Promise<boolean> {
+		if (!this.user) return false;
+
+		this.subscriber.on(`mainStream:${this.user.id}`, async data => {
 			switch (data.type) {
 				case 'notification': {
 					// Ignore notifications from instances the user has muted
@@ -61,5 +62,7 @@ export class MainChannel extends Channel {
 
 			this.send(data.type, data.body);
 		});
+
+		return true;
 	}
 }
diff --git a/packages/backend/src/server/api/stream/channels/user-list.ts b/packages/backend/src/server/api/stream/channels/user-list.ts
index ae6386855b..6df7e32005 100644
--- a/packages/backend/src/server/api/stream/channels/user-list.ts
+++ b/packages/backend/src/server/api/stream/channels/user-list.ts
@@ -45,8 +45,8 @@ export class UserListChannel extends Channel {
 	}
 
 	@bindThis
-	public async init(params: JsonObject) {
-		if (typeof params.listId !== 'string') return;
+	public async init(params: JsonObject): Promise<boolean> {
+		if (typeof params.listId !== 'string') return false;
 		this.listId = params.listId;
 		this.withFiles = !!(params.withFiles ?? false);
 		this.withRenotes = !!(params.withRenotes ?? true);
@@ -58,7 +58,7 @@ export class UserListChannel extends Channel {
 				userId: this.user!.id,
 			},
 		});
-		if (!listExist) return;
+		if (!listExist) return false;
 
 		// Subscribe stream
 		this.subscriber.on(`userListStream:${this.listId}`, this.send);
@@ -67,6 +67,8 @@ export class UserListChannel extends Channel {
 
 		this.updateListUsers();
 		this.listUsersClock = setInterval(this.updateListUsers, 5000);
+
+		return true;
 	}
 
 	@bindThis
diff --git a/packages/backend/src/types.ts b/packages/backend/src/types.ts
index 24654b0017..d3b2ec1eb0 100644
--- a/packages/backend/src/types.ts
+++ b/packages/backend/src/types.ts
@@ -414,3 +414,5 @@ export type FilterUnionByProperty<
 	Property extends string | number | symbol,
 	Condition,
 > = Union extends Record<Property, Condition> ? Union : never;
+
+export type Awaitable<T> = T | Promise<T>;