Feat: Chat (#15686)

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* Update types.ts

* Create 1742203321812-chat.js

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* Update room.vue

* Update home.vue

* Update home.vue

* Update ja-JP.yml

* Update index.d.ts

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* Update CHANGELOG.md

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* Update home.vue

* clean up

* Update misskey-js.api.md

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* lint fixes

* lint

* Update UserEntityService.ts

* search

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* 🎨

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* Update home.ownedRooms.vue

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* Update CHANGELOG.md

* Update style.scss

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* improve performance

* improve performance

* Update timeline.test.ts

64 files changed, 3517 insertions, 435 deletions

diff --git a/packages/backend/src/core/ChatService.ts b/packages/backend/src/core/ChatService.ts
new file mode 100644
index 0000000000..eece5d0da3
--- /dev/null
+++ b/packages/backend/src/core/ChatService.ts
@@ -0,0 +1,776 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import * as Redis from 'ioredis';
+import { Brackets } from 'typeorm';
+import { DI } from '@/di-symbols.js';
+import type { Config } from '@/config.js';
+import { QueueService } from '@/core/QueueService.js';
+import { IdService } from '@/core/IdService.js';
+import { GlobalEventService } from '@/core/GlobalEventService.js';
+import { UserEntityService } from '@/core/entities/UserEntityService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+import { ApRendererService } from '@/core/activitypub/ApRendererService.js';
+import { PushNotificationService } from '@/core/PushNotificationService.js';
+import { bindThis } from '@/decorators.js';
+import type { ChatApprovalsRepository, ChatMessagesRepository, ChatRoomInvitationsRepository, ChatRoomMembershipsRepository, ChatRoomsRepository, MiChatMessage, MiChatRoom, MiChatRoomMembership, MiDriveFile, MiUser, MutingsRepository, UsersRepository } from '@/models/_.js';
+import { UserBlockingService } from '@/core/UserBlockingService.js';
+import { QueryService } from '@/core/QueryService.js';
+import { RoleService } from '@/core/RoleService.js';
+import { UserFollowingService } from '@/core/UserFollowingService.js';
+import { MiChatRoomInvitation } from '@/models/ChatRoomInvitation.js';
+import { Packed } from '@/misc/json-schema.js';
+import { sqlLikeEscape } from '@/misc/sql-like-escape.js';
+import { CustomEmojiService } from '@/core/CustomEmojiService.js';
+import { emojiRegex } from '@/misc/emoji-regex.js';
+
+const MAX_ROOM_MEMBERS = 30;
+const MAX_REACTIONS_PER_MESSAGE = 100;
+const isCustomEmojiRegexp = /^:([\w+-]+)(?:@\.)?:$/;
+
+@Injectable()
+export class ChatService {
+	constructor(
+		@Inject(DI.config)
+		private config: Config,
+
+		@Inject(DI.redis)
+		private redisClient: Redis.Redis,
+
+		@Inject(DI.usersRepository)
+		private usersRepository: UsersRepository,
+
+		@Inject(DI.chatMessagesRepository)
+		private chatMessagesRepository: ChatMessagesRepository,
+
+		@Inject(DI.chatApprovalsRepository)
+		private chatApprovalsRepository: ChatApprovalsRepository,
+
+		@Inject(DI.chatRoomsRepository)
+		private chatRoomsRepository: ChatRoomsRepository,
+
+		@Inject(DI.chatRoomInvitationsRepository)
+		private chatRoomInvitationsRepository: ChatRoomInvitationsRepository,
+
+		@Inject(DI.chatRoomMembershipsRepository)
+		private chatRoomMembershipsRepository: ChatRoomMembershipsRepository,
+
+		@Inject(DI.mutingsRepository)
+		private mutingsRepository: MutingsRepository,
+
+		private userEntityService: UserEntityService,
+		private chatEntityService: ChatEntityService,
+		private idService: IdService,
+		private globalEventService: GlobalEventService,
+		private apRendererService: ApRendererService,
+		private queueService: QueueService,
+		private pushNotificationService: PushNotificationService,
+		private userBlockingService: UserBlockingService,
+		private queryService: QueryService,
+		private roleService: RoleService,
+		private userFollowingService: UserFollowingService,
+		private customEmojiService: CustomEmojiService,
+	) {
+	}
+
+	@bindThis
+	public async createMessageToUser(fromUser: { id: MiUser['id']; host: MiUser['host']; }, toUser: MiUser, params: {
+		text?: string | null;
+		file?: MiDriveFile | null;
+		uri?: string | null;
+	}): Promise<Packed<'ChatMessageLite'>> {
+		if (fromUser.id === toUser.id) {
+			throw new Error('yourself');
+		}
+
+		const approvals = await this.chatApprovalsRepository.createQueryBuilder('approval')
+			.where(new Brackets(qb => { // 自分が相手を許可しているか
+				qb.where('approval.userId = :fromUserId', { fromUserId: fromUser.id })
+					.andWhere('approval.otherId = :toUserId', { toUserId: toUser.id });
+			}))
+			.orWhere(new Brackets(qb => { // 相手が自分を許可しているか
+				qb.where('approval.userId = :toUserId', { toUserId: toUser.id })
+					.andWhere('approval.otherId = :fromUserId', { fromUserId: fromUser.id });
+			}))
+			.take(2)
+			.getMany();
+
+		const otherApprovedMe = approvals.some(approval => approval.userId === toUser.id);
+		const iApprovedOther = approvals.some(approval => approval.userId === fromUser.id);
+
+		if (!otherApprovedMe) {
+			if (toUser.chatScope === 'none') {
+				throw new Error('recipient is cannot chat (none)');
+			} else if (toUser.chatScope === 'followers') {
+				const isFollower = await this.userFollowingService.isFollowing(fromUser.id, toUser.id);
+				if (!isFollower) {
+					throw new Error('recipient is cannot chat (followers)');
+				}
+			} else if (toUser.chatScope === 'following') {
+				const isFollowing = await this.userFollowingService.isFollowing(toUser.id, fromUser.id);
+				if (!isFollowing) {
+					throw new Error('recipient is cannot chat (following)');
+				}
+			} else if (toUser.chatScope === 'mutual') {
+				const isMutual = await this.userFollowingService.isMutual(fromUser.id, toUser.id);
+				if (!isMutual) {
+					throw new Error('recipient is cannot chat (mutual)');
+				}
+			}
+		}
+
+		if (!(await this.roleService.getUserPolicies(toUser.id)).canChat) {
+			throw new Error('recipient is cannot chat (policy)');
+		}
+
+		const blocked = await this.userBlockingService.checkBlocked(toUser.id, fromUser.id);
+		if (blocked) {
+			throw new Error('blocked');
+		}
+
+		const message = {
+			id: this.idService.gen(),
+			fromUserId: fromUser.id,
+			toUserId: toUser.id,
+			text: params.text ? params.text.trim() : null,
+			fileId: params.file ? params.file.id : null,
+			reads: [],
+			uri: params.uri ?? null,
+		} satisfies Partial<MiChatMessage>;
+
+		const inserted = await this.chatMessagesRepository.insertOne(message);
+
+		// 相手を許可しておく
+		if (!iApprovedOther) {
+			this.chatApprovalsRepository.insertOne({
+				id: this.idService.gen(),
+				userId: fromUser.id,
+				otherId: toUser.id,
+			});
+		}
+
+		const packedMessage = await this.chatEntityService.packMessageLiteFor1on1(inserted);
+
+		if (this.userEntityService.isLocalUser(toUser)) {
+			const redisPipeline = this.redisClient.pipeline();
+			redisPipeline.set(`newUserChatMessageExists:${toUser.id}:${fromUser.id}`, message.id);
+			redisPipeline.sadd(`newChatMessagesExists:${toUser.id}`, `user:${fromUser.id}`);
+			redisPipeline.exec();
+		}
+
+		if (this.userEntityService.isLocalUser(fromUser)) {
+			// 自分のストリーム
+			this.globalEventService.publishChatUserStream(fromUser.id, toUser.id, 'message', packedMessage);
+		}
+
+		if (this.userEntityService.isLocalUser(toUser)) {
+			// 相手のストリーム
+			this.globalEventService.publishChatUserStream(toUser.id, fromUser.id, 'message', packedMessage);
+		}
+
+		// 3秒経っても既読にならなかったらイベント発行
+		if (this.userEntityService.isLocalUser(toUser)) {
+			setTimeout(async () => {
+				const marker = await this.redisClient.get(`newUserChatMessageExists:${toUser.id}:${fromUser.id}`);
+
+				if (marker == null) return; // 既読
+
+				const packedMessageForTo = await this.chatEntityService.packMessageDetailed(inserted, toUser);
+				this.globalEventService.publishMainStream(toUser.id, 'newChatMessage', packedMessageForTo);
+				//this.pushNotificationService.pushNotification(toUser.id, 'newChatMessage', packedMessageForTo);
+			}, 3000);
+		}
+
+		return packedMessage;
+	}
+
+	@bindThis
+	public async createMessageToRoom(fromUser: { id: MiUser['id']; host: MiUser['host']; }, toRoom: MiChatRoom, params: {
+		text?: string | null;
+		file?: MiDriveFile | null;
+		uri?: string | null;
+	}): Promise<Packed<'ChatMessageLite'>> {
+		const memberships = await this.chatRoomMembershipsRepository.findBy({ roomId: toRoom.id });
+
+		if (toRoom.ownerId !== fromUser.id && !memberships.some(member => member.userId === fromUser.id)) {
+			throw new Error('you are not a member of the room');
+		}
+
+		const message = {
+			id: this.idService.gen(),
+			fromUserId: fromUser.id,
+			toRoomId: toRoom.id,
+			text: params.text ? params.text.trim() : null,
+			fileId: params.file ? params.file.id : null,
+			reads: [],
+			uri: params.uri ?? null,
+		} satisfies Partial<MiChatMessage>;
+
+		const inserted = await this.chatMessagesRepository.insertOne(message);
+
+		const packedMessage = await this.chatEntityService.packMessageLiteForRoom(inserted);
+
+		this.globalEventService.publishChatRoomStream(toRoom.id, 'message', packedMessage);
+
+		const redisPipeline = this.redisClient.pipeline();
+		for (const membership of memberships) {
+			if (membership.isMuted) continue;
+
+			redisPipeline.set(`newRoomChatMessageExists:${membership.userId}:${toRoom.id}`, message.id);
+			redisPipeline.sadd(`newChatMessagesExists:${membership.userId}`, `room:${toRoom.id}`);
+		}
+		redisPipeline.exec();
+
+		// 3秒経っても既読にならなかったらイベント発行
+		setTimeout(async () => {
+			const redisPipeline = this.redisClient.pipeline();
+			for (const membership of memberships) {
+				redisPipeline.get(`newRoomChatMessageExists:${membership.userId}:${toRoom.id}`);
+			}
+			const markers = await redisPipeline.exec();
+			if (markers == null) throw new Error('redis error');
+
+			if (markers.every(marker => marker[1] == null)) return;
+
+			const packedMessageForTo = await this.chatEntityService.packMessageDetailed(inserted);
+
+			for (let i = 0; i < memberships.length; i++) {
+				const marker = markers[i][1];
+				if (marker == null) continue;
+
+				this.globalEventService.publishMainStream(memberships[i].userId, 'newChatMessage', packedMessageForTo);
+				//this.pushNotificationService.pushNotification(memberships[i].userId, 'newChatMessage', packedMessageForTo);
+			}
+		}, 3000);
+
+		return packedMessage;
+	}
+
+	@bindThis
+	public async readUserChatMessage(
+		readerId: MiUser['id'],
+		senderId: MiUser['id'],
+	): Promise<void> {
+		const redisPipeline = this.redisClient.pipeline();
+		redisPipeline.del(`newUserChatMessageExists:${readerId}:${senderId}`);
+		redisPipeline.srem(`newChatMessagesExists:${readerId}`, `user:${senderId}`);
+		await redisPipeline.exec();
+	}
+
+	@bindThis
+	public async readRoomChatMessage(
+		readerId: MiUser['id'],
+		roomId: MiChatRoom['id'],
+	): Promise<void> {
+		const redisPipeline = this.redisClient.pipeline();
+		redisPipeline.del(`newRoomChatMessageExists:${readerId}:${roomId}`);
+		redisPipeline.srem(`newChatMessagesExists:${readerId}`, `room:${roomId}`);
+		await redisPipeline.exec();
+	}
+
+	@bindThis
+	public findMessageById(messageId: MiChatMessage['id']) {
+		return this.chatMessagesRepository.findOneBy({ id: messageId });
+	}
+
+	@bindThis
+	public findMyMessageById(userId: MiUser['id'], messageId: MiChatMessage['id']) {
+		return this.chatMessagesRepository.findOneBy({ id: messageId, fromUserId: userId });
+	}
+
+	@bindThis
+	public async deleteMessage(message: MiChatMessage) {
+		await this.chatMessagesRepository.delete(message.id);
+
+		if (message.toUserId) {
+			const [fromUser, toUser] = await Promise.all([
+				this.usersRepository.findOneByOrFail({ id: message.fromUserId }),
+				this.usersRepository.findOneByOrFail({ id: message.toUserId }),
+			]);
+
+			if (this.userEntityService.isLocalUser(fromUser)) this.globalEventService.publishChatUserStream(message.fromUserId, message.toUserId, 'deleted', message.id);
+			if (this.userEntityService.isLocalUser(toUser)) this.globalEventService.publishChatUserStream(message.toUserId, message.fromUserId, 'deleted', message.id);
+
+			if (this.userEntityService.isLocalUser(fromUser) && this.userEntityService.isRemoteUser(toUser)) {
+				//const activity = this.apRendererService.addContext(this.apRendererService.renderDelete(this.apRendererService.renderTombstone(`${this.config.url}/notes/${message.id}`), fromUser));
+				//this.queueService.deliver(fromUser, activity, toUser.inbox);
+			}
+		} else if (message.toRoomId) {
+			this.globalEventService.publishChatRoomStream(message.toRoomId, 'deleted', message.id);
+		}
+	}
+
+	@bindThis
+	public async userTimeline(meId: MiUser['id'], otherId: MiUser['id'], limit: number, sinceId?: MiChatMessage['id'] | null, untilId?: MiChatMessage['id'] | null) {
+		const query = this.queryService.makePaginationQuery(this.chatMessagesRepository.createQueryBuilder('message'), sinceId, untilId)
+			.andWhere(new Brackets(qb => {
+				qb
+					.where(new Brackets(qb => {
+						qb
+							.where('message.fromUserId = :meId')
+							.andWhere('message.toUserId = :otherId');
+					}))
+					.orWhere(new Brackets(qb => {
+						qb
+							.where('message.fromUserId = :otherId')
+							.andWhere('message.toUserId = :meId');
+					}));
+			}))
+			.setParameter('meId', meId)
+			.setParameter('otherId', otherId);
+
+		const messages = await query.take(limit).getMany();
+
+		return messages;
+	}
+
+	@bindThis
+	public async roomTimeline(roomId: MiChatRoom['id'], limit: number, sinceId?: MiChatMessage['id'] | null, untilId?: MiChatMessage['id'] | null) {
+		const query = this.queryService.makePaginationQuery(this.chatMessagesRepository.createQueryBuilder('message'), sinceId, untilId)
+			.where('message.toRoomId = :roomId', { roomId })
+			.leftJoinAndSelect('message.file', 'file')
+			.leftJoinAndSelect('message.fromUser', 'fromUser');
+
+		const messages = await query.take(limit).getMany();
+
+		return messages;
+	}
+
+	@bindThis
+	public async userHistory(meId: MiUser['id'], limit: number): Promise<MiChatMessage[]> {
+		const history: MiChatMessage[] = [];
+
+		const mutingQuery = this.mutingsRepository.createQueryBuilder('muting')
+			.select('muting.muteeId')
+			.where('muting.muterId = :muterId', { muterId: meId });
+
+		for (let i = 0; i < limit; i++) {
+			const found = history.map(m => (m.fromUserId === meId) ? m.toUserId! : m.fromUserId!);
+
+			const query = this.chatMessagesRepository.createQueryBuilder('message')
+				.orderBy('message.id', 'DESC')
+				.where(new Brackets(qb => {
+					qb
+						.where('message.fromUserId = :meId', { meId: meId })
+						.orWhere('message.toUserId = :meId', { meId: meId });
+				}))
+				.andWhere('message.toRoomId IS NULL')
+				.andWhere(`message.fromUserId NOT IN (${ mutingQuery.getQuery() })`)
+				.andWhere(`message.toUserId NOT IN (${ mutingQuery.getQuery() })`);
+
+			if (found.length > 0) {
+				query.andWhere('message.fromUserId NOT IN (:...found)', { found: found });
+				query.andWhere('message.toUserId NOT IN (:...found)', { found: found });
+			}
+
+			query.setParameters(mutingQuery.getParameters());
+
+			const message = await query.getOne();
+
+			if (message) {
+				history.push(message);
+			} else {
+				break;
+			}
+		}
+
+		return history;
+	}
+
+	@bindThis
+	public async roomHistory(meId: MiUser['id'], limit: number): Promise<MiChatMessage[]> {
+		// TODO: 一回のクエリにまとめられるかも
+		const [memberRoomIds, ownedRoomIds] = await Promise.all([
+			this.chatRoomMembershipsRepository.findBy({
+				userId: meId,
+			}).then(xs => xs.map(x => x.roomId)),
+			this.chatRoomsRepository.findBy({
+				ownerId: meId,
+			}).then(xs => xs.map(x => x.id)),
+		]);
+
+		const roomIds = memberRoomIds.concat(ownedRoomIds);
+
+		if (memberRoomIds.length === 0 && ownedRoomIds.length === 0) {
+			return [];
+		}
+
+		const history: MiChatMessage[] = [];
+
+		for (let i = 0; i < limit; i++) {
+			const found = history.map(m => m.toRoomId!);
+
+			const query = this.chatMessagesRepository.createQueryBuilder('message')
+				.orderBy('message.id', 'DESC')
+				.where('message.toRoomId IN (:...roomIds)', { roomIds });
+
+			if (found.length > 0) {
+				query.andWhere('message.toRoomId NOT IN (:...found)', { found: found });
+			}
+
+			const message = await query.getOne();
+
+			if (message) {
+				history.push(message);
+			} else {
+				break;
+			}
+		}
+
+		return history;
+	}
+
+	@bindThis
+	public async getUserReadStateMap(userId: MiUser['id'], otherIds: MiUser['id'][]) {
+		const readStateMap: Record<MiUser['id'], boolean> = {};
+
+		const redisPipeline = this.redisClient.pipeline();
+
+		for (const otherId of otherIds) {
+			redisPipeline.get(`newUserChatMessageExists:${userId}:${otherId}`);
+		}
+
+		const markers = await redisPipeline.exec();
+		if (markers == null) throw new Error('redis error');
+
+		for (let i = 0; i < otherIds.length; i++) {
+			const marker = markers[i][1];
+			readStateMap[otherIds[i]] = marker == null;
+		}
+
+		return readStateMap;
+	}
+
+	@bindThis
+	public async getRoomReadStateMap(userId: MiUser['id'], roomIds: MiChatRoom['id'][]) {
+		const readStateMap: Record<MiChatRoom['id'], boolean> = {};
+
+		const redisPipeline = this.redisClient.pipeline();
+
+		for (const roomId of roomIds) {
+			redisPipeline.get(`newRoomChatMessageExists:${userId}:${roomId}`);
+		}
+
+		const markers = await redisPipeline.exec();
+		if (markers == null) throw new Error('redis error');
+
+		for (let i = 0; i < roomIds.length; i++) {
+			const marker = markers[i][1];
+			readStateMap[roomIds[i]] = marker == null;
+		}
+
+		return readStateMap;
+	}
+
+	@bindThis
+	public async hasUnreadMessages(userId: MiUser['id']) {
+		const card = await this.redisClient.scard(`newChatMessagesExists:${userId}`);
+		return card > 0;
+	}
+
+	@bindThis
+	public async createRoom(owner: MiUser, params: Partial<{
+		name: string;
+		description: string;
+	}>) {
+		const room = {
+			id: this.idService.gen(),
+			name: params.name,
+			description: params.description,
+			ownerId: owner.id,
+		} satisfies Partial<MiChatRoom>;
+
+		const created = await this.chatRoomsRepository.insertOne(room);
+
+		return created;
+	}
+
+	@bindThis
+	public async deleteRoom(room: MiChatRoom) {
+		await this.chatRoomsRepository.delete(room.id);
+	}
+
+	@bindThis
+	public async findMyRoomById(ownerId: MiUser['id'], roomId: MiChatRoom['id']) {
+		return this.chatRoomsRepository.findOneBy({ id: roomId, ownerId: ownerId });
+	}
+
+	@bindThis
+	public async findRoomById(roomId: MiChatRoom['id']) {
+		return this.chatRoomsRepository.findOne({ where: { id: roomId }, relations: ['owner'] });
+	}
+
+	@bindThis
+	public async isRoomMember(room: MiChatRoom, userId: MiUser['id']) {
+		if (room.ownerId === userId) return true;
+		const membership = await this.chatRoomMembershipsRepository.findOneBy({ roomId: room.id, userId });
+		return membership != null;
+	}
+
+	@bindThis
+	public async createRoomInvitation(inviterId: MiUser['id'], roomId: MiChatRoom['id'], inviteeId: MiUser['id']) {
+		if (inviterId === inviteeId) {
+			throw new Error('yourself');
+		}
+
+		const room = await this.chatRoomsRepository.findOneByOrFail({ id: roomId, ownerId: inviterId });
+
+		const existingInvitation = await this.chatRoomInvitationsRepository.findOneBy({ roomId, userId: inviteeId });
+		if (existingInvitation) {
+			throw new Error('already invited');
+		}
+
+		const membershipsCount = await this.chatRoomMembershipsRepository.countBy({ roomId });
+		if (membershipsCount >= MAX_ROOM_MEMBERS) {
+			throw new Error('room is full');
+		}
+
+		// TODO: cehck block
+
+		const invitation = {
+			id: this.idService.gen(),
+			roomId: room.id,
+			userId: inviteeId,
+		} satisfies Partial<MiChatRoomInvitation>;
+
+		const created = await this.chatRoomInvitationsRepository.insertOne(invitation);
+
+		return created;
+	}
+
+	@bindThis
+	public async getOwnedRoomsWithPagination(ownerId: MiUser['id'], limit: number, sinceId?: MiChatRoom['id'] | null, untilId?: MiChatRoom['id'] | null) {
+		const query = this.queryService.makePaginationQuery(this.chatRoomsRepository.createQueryBuilder('room'), sinceId, untilId)
+			.where('room.ownerId = :ownerId', { ownerId });
+
+		const rooms = await query.take(limit).getMany();
+
+		return rooms;
+	}
+
+	@bindThis
+	public async getReceivedRoomInvitationsWithPagination(userId: MiUser['id'], limit: number, sinceId?: MiChatRoomInvitation['id'] | null, untilId?: MiChatRoomInvitation['id'] | null) {
+		const query = this.queryService.makePaginationQuery(this.chatRoomInvitationsRepository.createQueryBuilder('invitation'), sinceId, untilId)
+			.where('invitation.userId = :userId', { userId })
+			.andWhere('invitation.ignored = FALSE');
+
+		const invitations = await query.take(limit).getMany();
+
+		return invitations;
+	}
+
+	@bindThis
+	public async joinToRoom(userId: MiUser['id'], roomId: MiChatRoom['id']) {
+		const invitation = await this.chatRoomInvitationsRepository.findOneByOrFail({ roomId, userId });
+
+		const membershipsCount = await this.chatRoomMembershipsRepository.countBy({ roomId });
+		if (membershipsCount >= MAX_ROOM_MEMBERS) {
+			throw new Error('room is full');
+		}
+
+		const membership = {
+			id: this.idService.gen(),
+			roomId: roomId,
+			userId: userId,
+		} satisfies Partial<MiChatRoomMembership>;
+
+		// TODO: transaction
+		await this.chatRoomMembershipsRepository.insertOne(membership);
+		await this.chatRoomInvitationsRepository.delete(invitation.id);
+	}
+
+	@bindThis
+	public async ignoreRoomInvitation(userId: MiUser['id'], roomId: MiChatRoom['id']) {
+		const invitation = await this.chatRoomInvitationsRepository.findOneByOrFail({ roomId, userId });
+		await this.chatRoomInvitationsRepository.update(invitation.id, { ignored: true });
+	}
+
+	@bindThis
+	public async leaveRoom(userId: MiUser['id'], roomId: MiChatRoom['id']) {
+		const membership = await this.chatRoomMembershipsRepository.findOneByOrFail({ roomId, userId });
+		await this.chatRoomMembershipsRepository.delete(membership.id);
+	}
+
+	@bindThis
+	public async muteRoom(userId: MiUser['id'], roomId: MiChatRoom['id'], mute: boolean) {
+		const membership = await this.chatRoomMembershipsRepository.findOneByOrFail({ roomId, userId });
+		await this.chatRoomMembershipsRepository.update(membership.id, { isMuted: mute });
+	}
+
+	@bindThis
+	public async updateRoom(room: MiChatRoom, params: {
+		name?: string;
+		description?: string;
+	}): Promise<MiChatRoom> {
+		return this.chatRoomsRepository.createQueryBuilder().update()
+			.set(params)
+			.where('id = :id', { id: room.id })
+			.returning('*')
+			.execute()
+			.then((response) => {
+				return response.raw[0];
+			});
+	}
+
+	@bindThis
+	public async getRoomMembershipsWithPagination(roomId: MiChatRoom['id'], limit: number, sinceId?: MiChatRoomMembership['id'] | null, untilId?: MiChatRoomMembership['id'] | null) {
+		const query = this.queryService.makePaginationQuery(this.chatRoomMembershipsRepository.createQueryBuilder('membership'), sinceId, untilId)
+			.where('membership.roomId = :roomId', { roomId });
+
+		const memberships = await query.take(limit).getMany();
+
+		return memberships;
+	}
+
+	@bindThis
+	public async searchMessages(meId: MiUser['id'], query: string, limit: number, params: {
+		userId?: MiUser['id'] | null;
+		roomId?: MiChatRoom['id'] | null;
+	}) {
+		const q = this.chatMessagesRepository.createQueryBuilder('message');
+
+		if (params.userId) {
+			q.andWhere(new Brackets(qb => {
+				qb
+					.where(new Brackets(qb => {
+						qb
+							.where('message.fromUserId = :meId')
+							.andWhere('message.toUserId = :otherId');
+					}))
+					.orWhere(new Brackets(qb => {
+						qb
+							.where('message.fromUserId = :otherId')
+							.andWhere('message.toUserId = :meId');
+					}));
+			}))
+				.setParameter('meId', meId)
+				.setParameter('otherId', params.userId);
+		} else if (params.roomId) {
+			q.where('message.toRoomId = :roomId', { roomId: params.roomId });
+		} else {
+			const membershipsQuery = this.chatRoomMembershipsRepository.createQueryBuilder('membership')
+				.select('membership.roomId')
+				.where('membership.userId = :meId', { meId: meId });
+
+			const ownedRoomsQuery = this.chatRoomsRepository.createQueryBuilder('room')
+				.select('room.id')
+				.where('room.ownerId = :meId', { meId });
+
+			q.andWhere(new Brackets(qb => {
+				qb
+					.where('message.fromUserId = :meId')
+					.orWhere('message.toUserId = :meId')
+					.orWhere(`message.toRoomId IN (${membershipsQuery.getQuery()})`)
+					.orWhere(`message.toRoomId IN (${ownedRoomsQuery.getQuery()})`);
+			}));
+
+			q.setParameters(membershipsQuery.getParameters());
+			q.setParameters(ownedRoomsQuery.getParameters());
+		}
+
+		q.andWhere('LOWER(message.text) LIKE :q', { q: `%${ sqlLikeEscape(query.toLowerCase()) }%` });
+
+		q.leftJoinAndSelect('message.file', 'file');
+		q.leftJoinAndSelect('message.fromUser', 'fromUser');
+		q.leftJoinAndSelect('message.toUser', 'toUser');
+		q.leftJoinAndSelect('message.toRoom', 'toRoom');
+		q.leftJoinAndSelect('toRoom.owner', 'toRoomOwner');
+
+		const messages = await q.orderBy('message.id', 'DESC').take(limit).getMany();
+
+		return messages;
+	}
+
+	@bindThis
+	public async react(messageId: MiChatMessage['id'], userId: MiUser['id'], reaction_: string) {
+		let reaction;
+
+		// TODO: ReactionServiceのやつと共通化
+		function normalize(x: string) {
+			const match = emojiRegex.exec(x);
+			if (match) {
+				// 合字を含む1つの絵文字
+				const unicode = match[0];
+
+				// 異体字セレクタ除去
+				return unicode.match('\u200d') ? unicode : unicode.replace(/\ufe0f/g, '');
+			} else {
+				throw new Error('invalid emoji');
+			}
+		}
+
+		const custom = reaction_.match(isCustomEmojiRegexp);
+
+		if (custom == null) {
+			reaction = normalize(reaction_);
+		} else {
+			const name = custom[1];
+			const emoji = (await this.customEmojiService.localEmojisCache.fetch()).get(name);
+
+			if (emoji == null) {
+				throw new Error('no such emoji');
+			} else {
+				reaction = `:${name}:`;
+			}
+		}
+
+		const message = await this.chatMessagesRepository.findOneByOrFail({ id: messageId });
+
+		if (message.fromUserId === userId) {
+			throw new Error('cannot react to own message');
+		}
+
+		if (message.toRoomId === null && message.toUserId !== userId) {
+			throw new Error('cannot react to others message');
+		}
+
+		if (message.reactions.length >= MAX_REACTIONS_PER_MESSAGE) {
+			throw new Error('too many reactions');
+		}
+
+		const room = message.toRoomId ? await this.chatRoomsRepository.findOneByOrFail({ id: message.toRoomId }) : null;
+
+		if (room) {
+			if (!await this.isRoomMember(room, userId)) {
+				throw new Error('cannot react to others message');
+			}
+		}
+
+		await this.chatMessagesRepository.createQueryBuilder().update()
+			.set({
+				reactions: () => `array_append("reactions", '${userId}/${reaction}')`,
+			})
+			.where('id = :id', { id: message.id })
+			.execute();
+
+		if (room) {
+			this.globalEventService.publishChatRoomStream(room.id, 'react', {
+				messageId: message.id,
+				user: await this.userEntityService.pack(userId),
+				reaction,
+			});
+		} else {
+			this.globalEventService.publishChatUserStream(message.fromUserId, message.toUserId!, 'react', {
+				messageId: message.id,
+				reaction,
+			});
+			this.globalEventService.publishChatUserStream(message.toUserId!, message.fromUserId, 'react', {
+				messageId: message.id,
+				reaction,
+			});
+		}
+	}
+
+	@bindThis
+	public async getMyMemberships(userId: MiUser['id'], limit: number, sinceId?: MiChatRoomMembership['id'] | null, untilId?: MiChatRoomMembership['id'] | null) {
+		const query = this.queryService.makePaginationQuery(this.chatRoomMembershipsRepository.createQueryBuilder('membership'), sinceId, untilId)
+			.where('membership.userId = :userId', { userId });
+
+		const memberships = await query.take(limit).getMany();
+
+		return memberships;
+	}
+}
diff --git a/packages/backend/src/core/CoreModule.ts b/packages/backend/src/core/CoreModule.ts
index dc85a23e5b..d8617e343c 100644
--- a/packages/backend/src/core/CoreModule.ts
+++ b/packages/backend/src/core/CoreModule.ts
@@ -44,7 +44,6 @@ import { ModerationLogService } from './ModerationLogService.js';
 import { NoteCreateService } from './NoteCreateService.js';
 import { NoteDeleteService } from './NoteDeleteService.js';
 import { NotePiningService } from './NotePiningService.js';
-import { NoteReadService } from './NoteReadService.js';
 import { NotificationService } from './NotificationService.js';
 import { PollService } from './PollService.js';
 import { PushNotificationService } from './PushNotificationService.js';
@@ -75,6 +74,7 @@ import { ClipService } from './ClipService.js';
 import { FeaturedService } from './FeaturedService.js';
 import { FanoutTimelineService } from './FanoutTimelineService.js';
 import { ChannelFollowingService } from './ChannelFollowingService.js';
+import { ChatService } from './ChatService.js';
 import { RegistryApiService } from './RegistryApiService.js';
 import { ReversiService } from './ReversiService.js';
 
@@ -100,6 +100,7 @@ import { AppEntityService } from './entities/AppEntityService.js';
 import { AuthSessionEntityService } from './entities/AuthSessionEntityService.js';
 import { BlockingEntityService } from './entities/BlockingEntityService.js';
 import { ChannelEntityService } from './entities/ChannelEntityService.js';
+import { ChatEntityService } from './entities/ChatEntityService.js';
 import { ClipEntityService } from './entities/ClipEntityService.js';
 import { DriveFileEntityService } from './entities/DriveFileEntityService.js';
 import { DriveFolderEntityService } from './entities/DriveFolderEntityService.js';
@@ -184,7 +185,6 @@ const $ModerationLogService: Provider = { provide: 'ModerationLogService', useEx
 const $NoteCreateService: Provider = { provide: 'NoteCreateService', useExisting: NoteCreateService };
 const $NoteDeleteService: Provider = { provide: 'NoteDeleteService', useExisting: NoteDeleteService };
 const $NotePiningService: Provider = { provide: 'NotePiningService', useExisting: NotePiningService };
-const $NoteReadService: Provider = { provide: 'NoteReadService', useExisting: NoteReadService };
 const $NotificationService: Provider = { provide: 'NotificationService', useExisting: NotificationService };
 const $PollService: Provider = { provide: 'PollService', useExisting: PollService };
 const $SystemAccountService: Provider = { provide: 'SystemAccountService', useExisting: SystemAccountService };
@@ -221,6 +221,7 @@ const $FeaturedService: Provider = { provide: 'FeaturedService', useExisting: Fe
 const $FanoutTimelineService: Provider = { provide: 'FanoutTimelineService', useExisting: FanoutTimelineService };
 const $FanoutTimelineEndpointService: Provider = { provide: 'FanoutTimelineEndpointService', useExisting: FanoutTimelineEndpointService };
 const $ChannelFollowingService: Provider = { provide: 'ChannelFollowingService', useExisting: ChannelFollowingService };
+const $ChatService: Provider = { provide: 'ChatService', useExisting: ChatService };
 const $RegistryApiService: Provider = { provide: 'RegistryApiService', useExisting: RegistryApiService };
 const $ReversiService: Provider = { provide: 'ReversiService', useExisting: ReversiService };
 
@@ -247,6 +248,7 @@ const $AppEntityService: Provider = { provide: 'AppEntityService', useExisting:
 const $AuthSessionEntityService: Provider = { provide: 'AuthSessionEntityService', useExisting: AuthSessionEntityService };
 const $BlockingEntityService: Provider = { provide: 'BlockingEntityService', useExisting: BlockingEntityService };
 const $ChannelEntityService: Provider = { provide: 'ChannelEntityService', useExisting: ChannelEntityService };
+const $ChatEntityService: Provider = { provide: 'ChatEntityService', useExisting: ChatEntityService };
 const $ClipEntityService: Provider = { provide: 'ClipEntityService', useExisting: ClipEntityService };
 const $DriveFileEntityService: Provider = { provide: 'DriveFileEntityService', useExisting: DriveFileEntityService };
 const $DriveFolderEntityService: Provider = { provide: 'DriveFolderEntityService', useExisting: DriveFolderEntityService };
@@ -333,7 +335,6 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		NoteCreateService,
 		NoteDeleteService,
 		NotePiningService,
-		NoteReadService,
 		NotificationService,
 		PollService,
 		SystemAccountService,
@@ -370,6 +371,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		FanoutTimelineService,
 		FanoutTimelineEndpointService,
 		ChannelFollowingService,
+		ChatService,
 		RegistryApiService,
 		ReversiService,
 
@@ -396,6 +398,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		AuthSessionEntityService,
 		BlockingEntityService,
 		ChannelEntityService,
+		ChatEntityService,
 		ClipEntityService,
 		DriveFileEntityService,
 		DriveFolderEntityService,
@@ -478,7 +481,6 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		$NoteCreateService,
 		$NoteDeleteService,
 		$NotePiningService,
-		$NoteReadService,
 		$NotificationService,
 		$PollService,
 		$SystemAccountService,
@@ -515,6 +517,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		$FanoutTimelineService,
 		$FanoutTimelineEndpointService,
 		$ChannelFollowingService,
+		$ChatService,
 		$RegistryApiService,
 		$ReversiService,
 
@@ -541,6 +544,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		$AuthSessionEntityService,
 		$BlockingEntityService,
 		$ChannelEntityService,
+		$ChatEntityService,
 		$ClipEntityService,
 		$DriveFileEntityService,
 		$DriveFolderEntityService,
@@ -624,7 +628,6 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		NoteCreateService,
 		NoteDeleteService,
 		NotePiningService,
-		NoteReadService,
 		NotificationService,
 		PollService,
 		SystemAccountService,
@@ -661,6 +664,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		FanoutTimelineService,
 		FanoutTimelineEndpointService,
 		ChannelFollowingService,
+		ChatService,
 		RegistryApiService,
 		ReversiService,
 
@@ -686,6 +690,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		AuthSessionEntityService,
 		BlockingEntityService,
 		ChannelEntityService,
+		ChatEntityService,
 		ClipEntityService,
 		DriveFileEntityService,
 		DriveFolderEntityService,
@@ -768,7 +773,6 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		$NoteCreateService,
 		$NoteDeleteService,
 		$NotePiningService,
-		$NoteReadService,
 		$NotificationService,
 		$PollService,
 		$SystemAccountService,
@@ -804,6 +808,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		$FanoutTimelineService,
 		$FanoutTimelineEndpointService,
 		$ChannelFollowingService,
+		$ChatService,
 		$RegistryApiService,
 		$ReversiService,
 
@@ -829,6 +834,7 @@ const $ApQuestionService: Provider = { provide: 'ApQuestionService', useExisting
 		$AuthSessionEntityService,
 		$BlockingEntityService,
 		$ChannelEntityService,
+		$ChatEntityService,
 		$ClipEntityService,
 		$DriveFileEntityService,
 		$DriveFolderEntityService,
diff --git a/packages/backend/src/core/GlobalEventService.ts b/packages/backend/src/core/GlobalEventService.ts
index 224fdabc4c..4da3b8bc78 100644
--- a/packages/backend/src/core/GlobalEventService.ts
+++ b/packages/backend/src/core/GlobalEventService.ts
@@ -20,7 +20,7 @@ import type { MiPage } from '@/models/Page.js';
 import type { MiWebhook } from '@/models/Webhook.js';
 import type { MiSystemWebhook } from '@/models/SystemWebhook.js';
 import type { MiMeta } from '@/models/Meta.js';
-import { MiAvatarDecoration, MiReversiGame, MiRole, MiRoleAssignment } from '@/models/_.js';
+import { MiAvatarDecoration, MiChatMessage, MiChatRoom, MiReversiGame, MiRole, MiRoleAssignment } from '@/models/_.js';
 import type { Packed } from '@/misc/json-schema.js';
 import { DI } from '@/di-symbols.js';
 import type { Config } from '@/config.js';
@@ -72,12 +72,8 @@ export interface MainEventTypes {
 	readAllNotifications: undefined;
 	notificationFlushed: undefined;
 	unreadNotification: Packed<'Notification'>;
-	unreadMention: MiNote['id'];
-	readAllUnreadMentions: undefined;
-	unreadSpecifiedNote: MiNote['id'];
-	readAllUnreadSpecifiedNotes: undefined;
-	readAllAntennas: undefined;
 	unreadAntenna: MiAntenna;
+	newChatMessage: Packed<'ChatMessage'>;
 	readAllAnnouncements: undefined;
 	myTokenRegenerated: undefined;
 	signin: {
@@ -163,6 +159,16 @@ export interface AdminEventTypes {
 	};
 }
 
+export interface ChatEventTypes {
+	message: Packed<'ChatMessageLite'>;
+	deleted: Packed<'ChatMessageLite'>['id'];
+	react: {
+		reaction: string;
+		user?: Packed<'UserLite'>;
+		messageId: MiChatMessage['id'];
+	};
+}
+
 export interface ReversiEventTypes {
 	matched: {
 		game: Packed<'ReversiGameDetailed'>;
@@ -202,7 +208,7 @@ export interface ReversiGameEventTypes {
 type Events<T extends object> = { [K in keyof T]: { type: K; body: T[K]; } };
 type EventUnionFromDictionary<
 	T extends object,
-	U = Events<T>
+	U = Events<T>,
 > = U[keyof U];
 
 type SerializedAll<T> = {
@@ -295,6 +301,14 @@ export type GlobalEvents = {
 		name: 'notesStream';
 		payload: Serialized<Packed<'Note'>>;
 	};
+	chat: {
+		name: `chatUserStream:${MiUser['id']}-${MiUser['id']}`;
+		payload: EventTypesToEventPayload<ChatEventTypes>;
+	};
+	chatRoom: {
+		name: `chatRoomStream:${MiChatRoom['id']}`;
+		payload: EventTypesToEventPayload<ChatEventTypes>;
+	};
 	reversi: {
 		name: `reversiStream:${MiUser['id']}`;
 		payload: EventTypesToEventPayload<ReversiEventTypes>;
@@ -394,6 +408,16 @@ export class GlobalEventService {
 	}
 
 	@bindThis
+	public publishChatUserStream<K extends keyof ChatEventTypes>(fromUserId: MiUser['id'], toUserId: MiUser['id'], type: K, value?: ChatEventTypes[K]): void {
+		this.publish(`chatUserStream:${fromUserId}-${toUserId}`, type, typeof value === 'undefined' ? null : value);
+	}
+
+	@bindThis
+	public publishChatRoomStream<K extends keyof ChatEventTypes>(toRoomId: MiChatRoom['id'], type: K, value?: ChatEventTypes[K]): void {
+		this.publish(`chatRoomStream:${toRoomId}`, type, typeof value === 'undefined' ? null : value);
+	}
+
+	@bindThis
 	public publishReversiStream<K extends keyof ReversiEventTypes>(userId: MiUser['id'], type: K, value?: ReversiEventTypes[K]): void {
 		this.publish(`reversiStream:${userId}`, type, typeof value === 'undefined' ? null : value);
 	}
diff --git a/packages/backend/src/core/NoteCreateService.ts b/packages/backend/src/core/NoteCreateService.ts
index 8a79908e82..8f416f398c 100644
--- a/packages/backend/src/core/NoteCreateService.ts
+++ b/packages/backend/src/core/NoteCreateService.ts
@@ -42,7 +42,6 @@ import { NoteEntityService } from '@/core/entities/NoteEntityService.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
 import { ApRendererService } from '@/core/activitypub/ApRendererService.js';
 import { ApDeliverManagerService } from '@/core/activitypub/ApDeliverManagerService.js';
-import { NoteReadService } from '@/core/NoteReadService.js';
 import { RemoteUserResolveService } from '@/core/RemoteUserResolveService.js';
 import { bindThis } from '@/decorators.js';
 import { DB_MAX_NOTE_TEXT_LENGTH } from '@/const.js';
@@ -199,7 +198,6 @@ export class NoteCreateService implements OnApplicationShutdown {
 		private globalEventService: GlobalEventService,
 		private queueService: QueueService,
 		private fanoutTimelineService: FanoutTimelineService,
-		private noteReadService: NoteReadService,
 		private notificationService: NotificationService,
 		private relayService: RelayService,
 		private federatedInstanceService: FederatedInstanceService,
@@ -582,31 +580,6 @@ export class NoteCreateService implements OnApplicationShutdown {
 		if (!silent) {
 			if (this.userEntityService.isLocalUser(user)) this.activeUsersChart.write(user);
 
-			// 未読通知を作成
-			if (data.visibility === 'specified') {
-				if (data.visibleUsers == null) throw new Error('invalid param');
-
-				for (const u of data.visibleUsers) {
-					// ローカルユーザーのみ
-					if (!this.userEntityService.isLocalUser(u)) continue;
-
-					this.noteReadService.insertNoteUnread(u.id, note, {
-						isSpecified: true,
-						isMentioned: false,
-					});
-				}
-			} else {
-				for (const u of mentionedUsers) {
-					// ローカルユーザーのみ
-					if (!this.userEntityService.isLocalUser(u)) continue;
-
-					this.noteReadService.insertNoteUnread(u.id, note, {
-						isSpecified: false,
-						isMentioned: true,
-					});
-				}
-			}
-
 			// Pack the note
 			const noteObj = await this.noteEntityService.pack(note, null, { skipHide: true, withReactionAndUserPairCache: true });
 
diff --git a/packages/backend/src/core/NoteReadService.ts b/packages/backend/src/core/NoteReadService.ts
deleted file mode 100644
index 181c9f7649..0000000000
--- a/packages/backend/src/core/NoteReadService.ts
+++ /dev/null
@@ -1,143 +0,0 @@
-/*
- * SPDX-FileCopyrightText: syuilo and misskey-project
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-
-import { setTimeout } from 'node:timers/promises';
-import { Inject, Injectable, OnApplicationShutdown } from '@nestjs/common';
-import { In } from 'typeorm';
-import { DI } from '@/di-symbols.js';
-import type { MiUser } from '@/models/User.js';
-import type { Packed } from '@/misc/json-schema.js';
-import type { MiNote } from '@/models/Note.js';
-import { IdService } from '@/core/IdService.js';
-import { GlobalEventService } from '@/core/GlobalEventService.js';
-import type { NoteUnreadsRepository, MutingsRepository, NoteThreadMutingsRepository } from '@/models/_.js';
-import { bindThis } from '@/decorators.js';
-import { trackPromise } from '@/misc/promise-tracker.js';
-
-@Injectable()
-export class NoteReadService implements OnApplicationShutdown {
-	#shutdownController = new AbortController();
-
-	constructor(
-		@Inject(DI.noteUnreadsRepository)
-		private noteUnreadsRepository: NoteUnreadsRepository,
-
-		@Inject(DI.mutingsRepository)
-		private mutingsRepository: MutingsRepository,
-
-		@Inject(DI.noteThreadMutingsRepository)
-		private noteThreadMutingsRepository: NoteThreadMutingsRepository,
-
-		private idService: IdService,
-		private globalEventService: GlobalEventService,
-	) {
-	}
-
-	@bindThis
-	public async insertNoteUnread(userId: MiUser['id'], note: MiNote, params: {
-		// NOTE: isSpecifiedがtrueならisMentionedは必ずfalse
-		isSpecified: boolean;
-		isMentioned: boolean;
-	}): Promise<void> {
-		//#region ミュートしているなら無視
-		const mute = await this.mutingsRepository.findBy({
-			muterId: userId,
-		});
-		if (mute.map(m => m.muteeId).includes(note.userId)) return;
-		//#endregion
-
-		// スレッドミュート
-		const isThreadMuted = await this.noteThreadMutingsRepository.exists({
-			where: {
-				userId: userId,
-				threadId: note.threadId ?? note.id,
-			},
-		});
-		if (isThreadMuted) return;
-
-		const unread = {
-			id: this.idService.gen(),
-			noteId: note.id,
-			userId: userId,
-			isSpecified: params.isSpecified,
-			isMentioned: params.isMentioned,
-			noteUserId: note.userId,
-		};
-
-		await this.noteUnreadsRepository.insert(unread);
-
-		// 2秒経っても既読にならなかったら「未読の投稿がありますよ」イベントを発行する
-		setTimeout(2000, 'unread note', { signal: this.#shutdownController.signal }).then(async () => {
-			const exist = await this.noteUnreadsRepository.exists({ where: { id: unread.id } });
-
-			if (!exist) return;
-
-			if (params.isMentioned) {
-				this.globalEventService.publishMainStream(userId, 'unreadMention', note.id);
-			}
-			if (params.isSpecified) {
-				this.globalEventService.publishMainStream(userId, 'unreadSpecifiedNote', note.id);
-			}
-		}, () => { /* aborted, ignore it */ });
-	}
-
-	@bindThis
-	public async read(
-		userId: MiUser['id'],
-		notes: (MiNote | Packed<'Note'>)[],
-	): Promise<void> {
-		if (notes.length === 0) return;
-
-		const noteIds = new Set<MiNote['id']>();
-
-		for (const note of notes) {
-			if (note.mentions && note.mentions.includes(userId)) {
-				noteIds.add(note.id);
-			} else if (note.visibleUserIds && note.visibleUserIds.includes(userId)) {
-				noteIds.add(note.id);
-			}
-		}
-
-		if (noteIds.size === 0) return;
-
-		// Remove the record
-		await this.noteUnreadsRepository.delete({
-			userId: userId,
-			noteId: In(Array.from(noteIds)),
-		});
-
-		// TODO: ↓まとめてクエリしたい
-
-		trackPromise(this.noteUnreadsRepository.countBy({
-			userId: userId,
-			isMentioned: true,
-		}).then(mentionsCount => {
-			if (mentionsCount === 0) {
-				// 全て既読になったイベントを発行
-				this.globalEventService.publishMainStream(userId, 'readAllUnreadMentions');
-			}
-		}));
-
-		trackPromise(this.noteUnreadsRepository.countBy({
-			userId: userId,
-			isSpecified: true,
-		}).then(specifiedCount => {
-			if (specifiedCount === 0) {
-				// 全て既読になったイベントを発行
-				this.globalEventService.publishMainStream(userId, 'readAllUnreadSpecifiedNotes');
-			}
-		}));
-	}
-
-	@bindThis
-	public dispose(): void {
-		this.#shutdownController.abort();
-	}
-
-	@bindThis
-	public onApplicationShutdown(signal?: string | undefined): void {
-		this.dispose();
-	}
-}
diff --git a/packages/backend/src/core/RoleService.ts b/packages/backend/src/core/RoleService.ts
index 01f3e0c116..86f8a5caa1 100644
--- a/packages/backend/src/core/RoleService.ts
+++ b/packages/backend/src/core/RoleService.ts
@@ -63,6 +63,7 @@ export type RolePolicies = {
 	canImportFollowing: boolean;
 	canImportMuting: boolean;
 	canImportUserLists: boolean;
+	canChat: boolean;
 };
 
 export const DEFAULT_POLICIES: RolePolicies = {
@@ -97,6 +98,7 @@ export const DEFAULT_POLICIES: RolePolicies = {
 	canImportFollowing: true,
 	canImportMuting: true,
 	canImportUserLists: true,
+	canChat: true,
 };
 
 @Injectable()
@@ -400,6 +402,7 @@ export class RoleService implements OnApplicationShutdown, OnModuleInit {
 			canImportFollowing: calc('canImportFollowing', vs => vs.some(v => v === true)),
 			canImportMuting: calc('canImportMuting', vs => vs.some(v => v === true)),
 			canImportUserLists: calc('canImportUserLists', vs => vs.some(v => v === true)),
+			canChat: calc('canChat', vs => vs.some(v => v === true)),
 		};
 	}
 
diff --git a/packages/backend/src/core/UserFollowingService.ts b/packages/backend/src/core/UserFollowingService.ts
index b98ca97ec9..e7a6be99fb 100644
--- a/packages/backend/src/core/UserFollowingService.ts
+++ b/packages/backend/src/core/UserFollowingService.ts
@@ -5,7 +5,7 @@
 
 import { Inject, Injectable, OnModuleInit } from '@nestjs/common';
 import { ModuleRef } from '@nestjs/core';
-import { IsNull } from 'typeorm';
+import { Brackets, IsNull } from 'typeorm';
 import type { MiLocalUser, MiPartialLocalUser, MiPartialRemoteUser, MiRemoteUser, MiUser } from '@/models/User.js';
 import { IdentifiableError } from '@/misc/identifiable-error.js';
 import { QueueService } from '@/core/QueueService.js';
@@ -736,4 +736,30 @@ export class UserFollowingService implements OnModuleInit {
 			.where('following.followerId = :followerId', { followerId: userId })
 			.getMany();
 	}
+
+	@bindThis
+	public isFollowing(followerId: MiUser['id'], followeeId: MiUser['id']) {
+		return this.followingsRepository.exists({
+			where: {
+				followerId,
+				followeeId,
+			},
+		});
+	}
+
+	@bindThis
+	public async isMutual(aUserId: MiUser['id'], bUserId: MiUser['id']) {
+		const count = await this.followingsRepository.createQueryBuilder('following')
+			.where(new Brackets(qb => {
+				qb.where('following.followerId = :aUserId', { aUserId })
+					.andWhere('following.followeeId = :bUserId', { bUserId });
+			}))
+			.orWhere(new Brackets(qb => {
+				qb.where('following.followerId = :bUserId', { bUserId })
+					.andWhere('following.followeeId = :aUserId', { aUserId });
+			}))
+			.getCount();
+
+		return count === 2;
+	}
 }
diff --git a/packages/backend/src/core/WebhookTestService.ts b/packages/backend/src/core/WebhookTestService.ts
index e1a7801bb1..a6198f7686 100644
--- a/packages/backend/src/core/WebhookTestService.ts
+++ b/packages/backend/src/core/WebhookTestService.ts
@@ -53,6 +53,7 @@ function generateDummyUser(override?: Partial<MiUser>): MiUser {
 		requireSigninToViewContents: false,
 		makeNotesFollowersOnlyBefore: null,
 		makeNotesHiddenBefore: null,
+		chatScope: 'mutual',
 		emojis: [],
 		score: 0,
 		host: null,
@@ -461,6 +462,7 @@ export class WebhookTestService {
 			publicReactions: true,
 			followersVisibility: 'public',
 			followingVisibility: 'public',
+			chatScope: 'mutual',
 			twoFactorEnabled: false,
 			usePasswordLessLogin: false,
 			securityKeys: false,
diff --git a/packages/backend/src/core/entities/ChatEntityService.ts b/packages/backend/src/core/entities/ChatEntityService.ts
new file mode 100644
index 0000000000..099a9e3ad2
--- /dev/null
+++ b/packages/backend/src/core/entities/ChatEntityService.ts
@@ -0,0 +1,376 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { DI } from '@/di-symbols.js';
+import type { MiUser, ChatMessagesRepository, MiChatMessage, ChatRoomsRepository, MiChatRoom, MiChatRoomInvitation, ChatRoomInvitationsRepository, MiChatRoomMembership, ChatRoomMembershipsRepository } from '@/models/_.js';
+import { awaitAll } from '@/misc/prelude/await-all.js';
+import type { Packed } from '@/misc/json-schema.js';
+import type { } from '@/models/Blocking.js';
+import { bindThis } from '@/decorators.js';
+import { IdService } from '@/core/IdService.js';
+import { UserEntityService } from './UserEntityService.js';
+import { DriveFileEntityService } from './DriveFileEntityService.js';
+import { In } from 'typeorm';
+
+@Injectable()
+export class ChatEntityService {
+	constructor(
+		@Inject(DI.chatMessagesRepository)
+		private chatMessagesRepository: ChatMessagesRepository,
+
+		@Inject(DI.chatRoomsRepository)
+		private chatRoomsRepository: ChatRoomsRepository,
+
+		@Inject(DI.chatRoomInvitationsRepository)
+		private chatRoomInvitationsRepository: ChatRoomInvitationsRepository,
+
+		@Inject(DI.chatRoomMembershipsRepository)
+		private chatRoomMembershipsRepository: ChatRoomMembershipsRepository,
+
+		private userEntityService: UserEntityService,
+		private driveFileEntityService: DriveFileEntityService,
+		private idService: IdService,
+	) {
+	}
+
+	@bindThis
+	public async packMessageDetailed(
+		src: MiChatMessage['id'] | MiChatMessage,
+		me?: { id: MiUser['id'] },
+		options?: {
+			_hint_?: {
+				packedFiles?: Map<MiChatMessage['fileId'], Packed<'DriveFile'> | null>;
+				packedUsers?: Map<MiChatMessage['id'], Packed<'UserLite'>>;
+				packedRooms?: Map<MiChatMessage['toRoomId'], Packed<'ChatRoom'> | null>;
+			};
+		},
+	): Promise<Packed<'ChatMessage'>> {
+		const packedUsers = options?._hint_?.packedUsers;
+		const packedFiles = options?._hint_?.packedFiles;
+		const packedRooms = options?._hint_?.packedRooms;
+
+		const message = typeof src === 'object' ? src : await this.chatMessagesRepository.findOneByOrFail({ id: src });
+
+		const reactions: { user: Packed<'UserLite'>; reaction: string; }[] = [];
+
+		for (const record of message.reactions) {
+			const [userId, reaction] = record.split('/');
+			reactions.push({
+				user: packedUsers?.get(userId) ?? await this.userEntityService.pack(userId),
+				reaction,
+			});
+		}
+
+		return {
+			id: message.id,
+			createdAt: this.idService.parse(message.id).date.toISOString(),
+			text: message.text,
+			fromUserId: message.fromUserId,
+			fromUser: packedUsers?.get(message.fromUserId) ?? await this.userEntityService.pack(message.fromUser ?? message.fromUserId, me),
+			toUserId: message.toUserId,
+			toUser: message.toUserId ? (packedUsers?.get(message.toUserId) ?? await this.userEntityService.pack(message.toUser ?? message.toUserId, me)) : undefined,
+			toRoomId: message.toRoomId,
+			toRoom: message.toRoomId ? (packedRooms?.get(message.toRoomId) ?? await this.packRoom(message.toRoom ?? message.toRoomId, me)) : undefined,
+			fileId: message.fileId,
+			file: message.fileId ? (packedFiles?.get(message.fileId) ?? await this.driveFileEntityService.pack(message.file ?? message.fileId)) : null,
+			reactions,
+		};
+	}
+
+	@bindThis
+	public async packMessagesDetailed(
+		messages: MiChatMessage[],
+		me: { id: MiUser['id'] },
+	) {
+		if (messages.length === 0) return [];
+
+		const excludeMe = (x: MiUser | string) => {
+			if (typeof x === 'string') {
+				return x !== me.id;
+			} else {
+				return x.id !== me.id;
+			}
+		};
+
+		const users = [
+			...messages.map((m) => m.fromUser ?? m.fromUserId).filter(excludeMe),
+			...messages.map((m) => m.toUser ?? m.toUserId).filter(x => x != null).filter(excludeMe),
+		];
+
+		const reactedUserIds = messages.flatMap(x => x.reactions.map(r => r.split('/')[0]));
+
+		for (const reactedUserId of reactedUserIds) {
+			if (!users.some(x => typeof x === 'string' ? x === reactedUserId : x.id === reactedUserId)) {
+				users.push(reactedUserId);
+			}
+		}
+
+		const [packedUsers, packedFiles, packedRooms] = await Promise.all([
+			this.userEntityService.packMany(users, me)
+				.then(users => new Map(users.map(u => [u.id, u]))),
+			this.driveFileEntityService.packMany(messages.map(m => m.file).filter(x => x != null))
+				.then(files => new Map(files.map(f => [f.id, f]))),
+			this.packRooms(messages.map(m => m.toRoom ?? m.toRoomId).filter(x => x != null), me)
+				.then(rooms => new Map(rooms.map(r => [r.id, r]))),
+		]);
+
+		return Promise.all(messages.map(message => this.packMessageDetailed(message, me, { _hint_: { packedUsers, packedFiles, packedRooms } })));
+	}
+
+	@bindThis
+	public async packMessageLiteFor1on1(
+		src: MiChatMessage['id'] | MiChatMessage,
+		options?: {
+			_hint_?: {
+				packedFiles: Map<MiChatMessage['fileId'], Packed<'DriveFile'> | null>;
+			};
+		},
+	): Promise<Packed<'ChatMessageLite'>> {
+		const packedFiles = options?._hint_?.packedFiles;
+
+		const message = typeof src === 'object' ? src : await this.chatMessagesRepository.findOneByOrFail({ id: src });
+
+		const reactions: { reaction: string; }[] = [];
+
+		for (const record of message.reactions) {
+			const [userId, reaction] = record.split('/');
+			reactions.push({
+				reaction,
+			});
+		}
+
+		return {
+			id: message.id,
+			createdAt: this.idService.parse(message.id).date.toISOString(),
+			text: message.text,
+			fromUserId: message.fromUserId,
+			toUserId: message.toUserId,
+			fileId: message.fileId,
+			file: message.fileId ? (packedFiles?.get(message.fileId) ?? await this.driveFileEntityService.pack(message.file ?? message.fileId)) : null,
+			reactions,
+		};
+	}
+
+	@bindThis
+	public async packMessagesLiteFor1on1(
+		messages: MiChatMessage[],
+	) {
+		if (messages.length === 0) return [];
+
+		const [packedFiles] = await Promise.all([
+			this.driveFileEntityService.packMany(messages.map(m => m.file).filter(x => x != null))
+				.then(files => new Map(files.map(f => [f.id, f]))),
+		]);
+
+		return Promise.all(messages.map(message => this.packMessageLiteFor1on1(message, { _hint_: { packedFiles } })));
+	}
+
+	@bindThis
+	public async packMessageLiteForRoom(
+		src: MiChatMessage['id'] | MiChatMessage,
+		options?: {
+			_hint_?: {
+				packedFiles: Map<MiChatMessage['fileId'], Packed<'DriveFile'> | null>;
+				packedUsers: Map<MiUser['id'], Packed<'UserLite'>>;
+			};
+		},
+	): Promise<Packed<'ChatMessageLite'>> {
+		const packedFiles = options?._hint_?.packedFiles;
+		const packedUsers = options?._hint_?.packedUsers;
+
+		const message = typeof src === 'object' ? src : await this.chatMessagesRepository.findOneByOrFail({ id: src });
+
+		const reactions: { user: Packed<'UserLite'>; reaction: string; }[] = [];
+
+		for (const record of message.reactions) {
+			const [userId, reaction] = record.split('/');
+			reactions.push({
+				user: packedUsers?.get(userId) ?? await this.userEntityService.pack(userId),
+				reaction,
+			});
+		}
+
+		return {
+			id: message.id,
+			createdAt: this.idService.parse(message.id).date.toISOString(),
+			text: message.text,
+			fromUserId: message.fromUserId,
+			fromUser: packedUsers?.get(message.fromUserId) ?? await this.userEntityService.pack(message.fromUser ?? message.fromUserId),
+			toRoomId: message.toRoomId,
+			fileId: message.fileId,
+			file: message.fileId ? (packedFiles?.get(message.fileId) ?? await this.driveFileEntityService.pack(message.file ?? message.fileId)) : null,
+			reactions,
+		};
+	}
+
+	@bindThis
+	public async packMessagesLiteForRoom(
+		messages: MiChatMessage[],
+	) {
+		if (messages.length === 0) return [];
+
+		const users = messages.map(x => x.fromUser ?? x.fromUserId);
+		const reactedUserIds = messages.flatMap(x => x.reactions.map(r => r.split('/')[0]));
+
+		for (const reactedUserId of reactedUserIds) {
+			if (!users.some(x => typeof x === 'string' ? x === reactedUserId : x.id === reactedUserId)) {
+				users.push(reactedUserId);
+			}
+		}
+
+		const [packedUsers, packedFiles] = await Promise.all([
+			this.userEntityService.packMany(users)
+				.then(users => new Map(users.map(u => [u.id, u]))),
+			this.driveFileEntityService.packMany(messages.map(m => m.file).filter(x => x != null))
+				.then(files => new Map(files.map(f => [f.id, f]))),
+		]);
+
+		return Promise.all(messages.map(message => this.packMessageLiteForRoom(message, { _hint_: { packedFiles, packedUsers } })));
+	}
+
+	@bindThis
+	public async packRoom(
+		src: MiChatRoom['id'] | MiChatRoom,
+		me?: { id: MiUser['id'] },
+		options?: {
+			_hint_?: {
+				packedOwners: Map<MiChatRoom['id'], Packed<'UserLite'>>;
+				memberships?: Map<MiChatRoom['id'], MiChatRoomMembership | null | undefined>;
+			};
+		},
+	): Promise<Packed<'ChatRoom'>> {
+		const room = typeof src === 'object' ? src : await this.chatRoomsRepository.findOneByOrFail({ id: src });
+
+		const membership = me && me.id !== room.ownerId ? (options?._hint_?.memberships?.get(room.id) ?? await this.chatRoomMembershipsRepository.findOneBy({ roomId: room.id, userId: me.id })) : null;
+
+		return {
+			id: room.id,
+			createdAt: this.idService.parse(room.id).date.toISOString(),
+			name: room.name,
+			description: room.description,
+			ownerId: room.ownerId,
+			owner: options?._hint_?.packedOwners.get(room.ownerId) ?? await this.userEntityService.pack(room.owner ?? room.ownerId, me),
+			isMuted: membership != null ? membership.isMuted : false,
+		};
+	}
+
+	@bindThis
+	public async packRooms(
+		rooms: (MiChatRoom | MiChatRoom['id'])[],
+		me: { id: MiUser['id'] },
+	) {
+		if (rooms.length === 0) return [];
+
+		const _rooms = rooms.filter((room): room is MiChatRoom => typeof room !== 'string');
+		if (_rooms.length !== rooms.length) {
+			_rooms.push(
+				...await this.chatRoomsRepository.find({
+					where: {
+						id: In(rooms.filter((room): room is string => typeof room === 'string')),
+					},
+					relations: ['owner'],
+				}),
+			);
+		}
+
+		const owners = _rooms.map(x => x.owner ?? x.ownerId);
+
+		const [packedOwners, memberships] = await Promise.all([
+			this.userEntityService.packMany(owners, me)
+				.then(users => new Map(users.map(u => [u.id, u]))),
+			this.chatRoomMembershipsRepository.find({
+				where: {
+					roomId: In(_rooms.map(x => x.id)),
+					userId: me.id,
+				},
+			}).then(memberships => new Map(_rooms.map(r => [r.id, memberships.find(m => m.roomId === r.id)]))),
+		]);
+
+		return Promise.all(_rooms.map(room => this.packRoom(room, me, { _hint_: { packedOwners, memberships } })));
+	}
+
+	@bindThis
+	public async packRoomInvitation(
+		src: MiChatRoomInvitation['id'] | MiChatRoomInvitation,
+		me: { id: MiUser['id'] },
+		options?: {
+			_hint_?: {
+				packedRooms: Map<MiChatRoomInvitation['roomId'], Packed<'ChatRoom'>>;
+				packedUsers: Map<MiChatRoomInvitation['id'], Packed<'UserLite'>>;
+			};
+		},
+	): Promise<Packed<'ChatRoomInvitation'>> {
+		const invitation = typeof src === 'object' ? src : await this.chatRoomInvitationsRepository.findOneByOrFail({ id: src });
+
+		return {
+			id: invitation.id,
+			createdAt: this.idService.parse(invitation.id).date.toISOString(),
+			roomId: invitation.roomId,
+			room: options?._hint_?.packedRooms.get(invitation.roomId) ?? await this.packRoom(invitation.room ?? invitation.roomId, me),
+			userId: invitation.userId,
+			user: options?._hint_?.packedUsers.get(invitation.userId) ?? await this.userEntityService.pack(invitation.user ?? invitation.userId, me),
+		};
+	}
+
+	@bindThis
+	public async packRoomInvitations(
+		invitations: MiChatRoomInvitation[],
+		me: { id: MiUser['id'] },
+	) {
+		if (invitations.length === 0) return [];
+
+		return Promise.all(invitations.map(invitation => this.packRoomInvitation(invitation, me)));
+	}
+
+	@bindThis
+	public async packRoomMembership(
+		src: MiChatRoomMembership['id'] | MiChatRoomMembership,
+		me: { id: MiUser['id'] },
+		options?: {
+			populateUser?: boolean;
+			populateRoom?: boolean;
+			_hint_?: {
+				packedRooms: Map<MiChatRoomMembership['roomId'], Packed<'ChatRoom'>>;
+				packedUsers: Map<MiChatRoomMembership['id'], Packed<'UserLite'>>;
+			};
+		},
+	): Promise<Packed<'ChatRoomMembership'>> {
+		const membership = typeof src === 'object' ? src : await this.chatRoomMembershipsRepository.findOneByOrFail({ id: src });
+
+		return {
+			id: membership.id,
+			createdAt: this.idService.parse(membership.id).date.toISOString(),
+			userId: membership.userId,
+			user: options?.populateUser ? (options._hint_?.packedUsers.get(membership.userId) ?? await this.userEntityService.pack(membership.user ?? membership.userId, me)) : undefined,
+			roomId: membership.roomId,
+			room: options?.populateRoom ? (options._hint_?.packedRooms.get(membership.roomId) ?? await this.packRoom(membership.room ?? membership.roomId, me)) : undefined,
+		};
+	}
+
+	@bindThis
+	public async packRoomMemberships(
+		memberships: MiChatRoomMembership[],
+		me: { id: MiUser['id'] },
+		options: {
+			populateUser?: boolean;
+			populateRoom?: boolean;
+		} = {},
+	) {
+		if (memberships.length === 0) return [];
+
+		const users = memberships.map(x => x.user ?? x.userId);
+		const rooms = memberships.map(x => x.room ?? x.roomId);
+
+		const [packedUsers, packedRooms] = await Promise.all([
+			this.userEntityService.packMany(users, me)
+				.then(users => new Map(users.map(u => [u.id, u]))),
+			this.packRooms(rooms, me)
+				.then(rooms => new Map(rooms.map(r => [r.id, r]))),
+		]);
+
+		return Promise.all(memberships.map(membership => this.packRoomMembership(membership, me, { ...options, _hint_: { packedUsers, packedRooms } })));
+	}
+}
diff --git a/packages/backend/src/core/entities/UserEntityService.ts b/packages/backend/src/core/entities/UserEntityService.ts
index 69f698d9cb..92a684dc1a 100644
--- a/packages/backend/src/core/entities/UserEntityService.ts
+++ b/packages/backend/src/core/entities/UserEntityService.ts
@@ -32,7 +32,6 @@ import type {
 	MiUserNotePining,
 	MiUserProfile,
 	MutingsRepository,
-	NoteUnreadsRepository,
 	RenoteMutingsRepository,
 	UserMemoRepository,
 	UserNotePiningsRepository,
@@ -48,9 +47,9 @@ import { IdService } from '@/core/IdService.js';
 import type { AnnouncementService } from '@/core/AnnouncementService.js';
 import type { CustomEmojiService } from '@/core/CustomEmojiService.js';
 import { AvatarDecorationService } from '@/core/AvatarDecorationService.js';
+import { ChatService } from '@/core/ChatService.js';
 import type { OnModuleInit } from '@nestjs/common';
 import type { NoteEntityService } from './NoteEntityService.js';
-import type { DriveFileEntityService } from './DriveFileEntityService.js';
 import type { PageEntityService } from './PageEntityService.js';
 
 const Ajv = _Ajv.default;
@@ -94,6 +93,7 @@ export class UserEntityService implements OnModuleInit {
 	private federatedInstanceService: FederatedInstanceService;
 	private idService: IdService;
 	private avatarDecorationService: AvatarDecorationService;
+	private chatService: ChatService;
 
 	constructor(
 		private moduleRef: ModuleRef,
@@ -128,9 +128,6 @@ export class UserEntityService implements OnModuleInit {
 		@Inject(DI.renoteMutingsRepository)
 		private renoteMutingsRepository: RenoteMutingsRepository,
 
-		@Inject(DI.noteUnreadsRepository)
-		private noteUnreadsRepository: NoteUnreadsRepository,
-
 		@Inject(DI.userNotePiningsRepository)
 		private userNotePiningsRepository: UserNotePiningsRepository,
 
@@ -152,6 +149,7 @@ export class UserEntityService implements OnModuleInit {
 		this.federatedInstanceService = this.moduleRef.get('FederatedInstanceService');
 		this.idService = this.moduleRef.get('IdService');
 		this.avatarDecorationService = this.moduleRef.get('AvatarDecorationService');
+		this.chatService = this.moduleRef.get('ChatService');
 	}
 
 	//#region Validators
@@ -558,6 +556,7 @@ export class UserEntityService implements OnModuleInit {
 				publicReactions: this.isLocalUser(user) ? profile!.publicReactions : false, // https://github.com/misskey-dev/misskey/issues/12964
 				followersVisibility: profile!.followersVisibility,
 				followingVisibility: profile!.followingVisibility,
+				chatScope: user.chatScope,
 				roles: this.roleService.getUserRoles(user.id).then(roles => roles.filter(role => role.isPublic).sort((a, b) => b.displayOrder - a.displayOrder).map(role => ({
 					id: role.id,
 					name: role.name,
@@ -598,14 +597,9 @@ export class UserEntityService implements OnModuleInit {
 				isDeleted: user.isDeleted,
 				twoFactorBackupCodesStock: profile?.twoFactorBackupSecret?.length === 5 ? 'full' : (profile?.twoFactorBackupSecret?.length ?? 0) > 0 ? 'partial' : 'none',
 				hideOnlineStatus: user.hideOnlineStatus,
-				hasUnreadSpecifiedNotes: this.noteUnreadsRepository.count({
-					where: { userId: user.id, isSpecified: true },
-					take: 1,
-				}).then(count => count > 0),
-				hasUnreadMentions: this.noteUnreadsRepository.count({
-					where: { userId: user.id, isMentioned: true },
-					take: 1,
-				}).then(count => count > 0),
+				hasUnreadSpecifiedNotes: false, // 後方互換性のため
+				hasUnreadMentions: false, // 後方互換性のため
+				hasUnreadChatMessages: this.chatService.hasUnreadMessages(user.id),
 				hasUnreadAnnouncement: unreadAnnouncements!.length > 0,
 				unreadAnnouncements,
 				hasUnreadAntenna: this.getHasUnreadAntenna(user.id),
diff --git a/packages/backend/src/di-symbols.ts b/packages/backend/src/di-symbols.ts
index a306aac1a1..77d2838e09 100644
--- a/packages/backend/src/di-symbols.ts
+++ b/packages/backend/src/di-symbols.ts
@@ -24,7 +24,6 @@ export const DI = {
 	noteFavoritesRepository: Symbol('noteFavoritesRepository'),
 	noteThreadMutingsRepository: Symbol('noteThreadMutingsRepository'),
 	noteReactionsRepository: Symbol('noteReactionsRepository'),
-	noteUnreadsRepository: Symbol('noteUnreadsRepository'),
 	pollsRepository: Symbol('pollsRepository'),
 	pollVotesRepository: Symbol('pollVotesRepository'),
 	userProfilesRepository: Symbol('userProfilesRepository'),
@@ -83,6 +82,11 @@ export const DI = {
 	flashsRepository: Symbol('flashsRepository'),
 	flashLikesRepository: Symbol('flashLikesRepository'),
 	userMemosRepository: Symbol('userMemosRepository'),
+	chatMessagesRepository: Symbol('chatMessagesRepository'),
+	chatApprovalsRepository: Symbol('chatApprovalsRepository'),
+	chatRoomsRepository: Symbol('chatRoomsRepository'),
+	chatRoomMembershipsRepository: Symbol('chatRoomMembershipsRepository'),
+	chatRoomInvitationsRepository: Symbol('chatRoomInvitationsRepository'),
 	bubbleGameRecordsRepository: Symbol('bubbleGameRecordsRepository'),
 	reversiGamesRepository: Symbol('reversiGamesRepository'),
 	//#endregion
diff --git a/packages/backend/src/misc/json-schema.ts b/packages/backend/src/misc/json-schema.ts
index 100fb69585..bc9308ca9b 100644
--- a/packages/backend/src/misc/json-schema.ts
+++ b/packages/backend/src/misc/json-schema.ts
@@ -63,6 +63,10 @@ import {
 } from '@/models/json-schema/meta.js';
 import { packedSystemWebhookSchema } from '@/models/json-schema/system-webhook.js';
 import { packedAbuseReportNotificationRecipientSchema } from '@/models/json-schema/abuse-report-notification-recipient.js';
+import { packedChatMessageSchema, packedChatMessageLiteSchema } from '@/models/json-schema/chat-message.js';
+import { packedChatRoomSchema } from '@/models/json-schema/chat-room.js';
+import { packedChatRoomInvitationSchema } from '@/models/json-schema/chat-room-invitation.js';
+import { packedChatRoomMembershipSchema } from '@/models/json-schema/chat-room-membership.js';
 
 export const refs = {
 	UserLite: packedUserLiteSchema,
@@ -120,6 +124,11 @@ export const refs = {
 	MetaDetailed: packedMetaDetailedSchema,
 	SystemWebhook: packedSystemWebhookSchema,
 	AbuseReportNotificationRecipient: packedAbuseReportNotificationRecipientSchema,
+	ChatMessage: packedChatMessageSchema,
+	ChatMessageLite: packedChatMessageLiteSchema,
+	ChatRoom: packedChatRoomSchema,
+	ChatRoomInvitation: packedChatRoomInvitationSchema,
+	ChatRoomMembership: packedChatRoomMembershipSchema,
 };
 
 export type Packed<x extends keyof typeof refs> = SchemaType<typeof refs[x]>;
@@ -171,11 +180,11 @@ export interface Schema extends OfSchema {
 
 type RequiredPropertyNames<s extends Obj> = {
 	[K in keyof s]:
-		// K is not optional
-		s[K]['optional'] extends false ? K :
-		// K has default value
-		s[K]['default'] extends null | string | number | boolean | Record<string, unknown> ? K :
-		never
+	// K is not optional
+	s[K]['optional'] extends false ? K :
+	// K has default value
+	s[K]['default'] extends null | string | number | boolean | Record<string, unknown> ? K :
+	never
 }[keyof s];
 
 export type Obj = Record<string, Schema>;
@@ -214,18 +223,18 @@ type ObjectSchemaTypeDef<p extends Schema> =
 		p['anyOf'] extends ReadonlyArray<Schema> ? p['anyOf'][number]['required'] extends ReadonlyArray<keyof p['properties']> ?
 			UnionObjType<p['properties'], NonNullable<p['anyOf'][number]['required']>> & ObjType<p['properties'], NonNullable<p['required']>>
 			: never
-			: ObjType<p['properties'], NonNullable<p['required']>>
-	:
-	p['anyOf'] extends ReadonlyArray<Schema> ? never : // see CONTRIBUTING.md
-	p['allOf'] extends ReadonlyArray<Schema> ? UnionToIntersection<UnionSchemaType<p['allOf']>> :
-	p['additionalProperties'] extends true ? Record<string, any> :
-	p['additionalProperties'] extends Schema ?
-		p['additionalProperties'] extends infer AdditionalProperties ?
-			AdditionalProperties extends Schema ?
-				Record<string, SchemaType<AdditionalProperties>> :
+		: ObjType<p['properties'], NonNullable<p['required']>>
+		:
+		p['anyOf'] extends ReadonlyArray<Schema> ? never : // see CONTRIBUTING.md
+		p['allOf'] extends ReadonlyArray<Schema> ? UnionToIntersection<UnionSchemaType<p['allOf']>> :
+		p['additionalProperties'] extends true ? Record<string, any> :
+		p['additionalProperties'] extends Schema ?
+			p['additionalProperties'] extends infer AdditionalProperties ?
+				AdditionalProperties extends Schema ?
+					Record<string, SchemaType<AdditionalProperties>> :
+					never :
 				never :
-			never :
-	any;
+			any;
 
 type ObjectSchemaType<p extends Schema> = NullOrUndefined<p, ObjectSchemaTypeDef<p>>;
 
@@ -235,30 +244,30 @@ export type SchemaTypeDef<p extends Schema> =
 	p['type'] extends 'number' ? number :
 	p['type'] extends 'string' ? (
 		p['enum'] extends readonly (string | null)[] ?
-		p['enum'][number] :
-		p['format'] extends 'date-time' ? string : // Dateにする？？
-		string
+			p['enum'][number] :
+			p['format'] extends 'date-time' ? string : // Dateにする？？
+			string
 	) :
-	p['type'] extends 'boolean' ? boolean :
-	p['type'] extends 'object' ? ObjectSchemaTypeDef<p> :
-	p['type'] extends 'array' ? (
-		p['items'] extends OfSchema ? (
-			p['items']['anyOf'] extends ReadonlyArray<Schema> ? UnionSchemaType<NonNullable<p['items']['anyOf']>>[] :
-			p['items']['oneOf'] extends ReadonlyArray<Schema> ? ArrayUnion<UnionSchemaType<NonNullable<p['items']['oneOf']>>> :
-			p['items']['allOf'] extends ReadonlyArray<Schema> ? UnionToIntersection<UnionSchemaType<NonNullable<p['items']['allOf']>>>[] :
-			never
-		) :
-		p['prefixItems'] extends ReadonlyArray<Schema> ? (
-			p['items'] extends NonNullable<Schema> ? [...ArrayToTuple<p['prefixItems']>, ...SchemaType<p['items']>[]] :
-			p['items'] extends false ? ArrayToTuple<p['prefixItems']> :
-			p['unevaluatedItems'] extends false ? ArrayToTuple<p['prefixItems']> :
-			[...ArrayToTuple<p['prefixItems']>, ...unknown[]]
+		p['type'] extends 'boolean' ? boolean :
+		p['type'] extends 'object' ? ObjectSchemaTypeDef<p> :
+		p['type'] extends 'array' ? (
+			p['items'] extends OfSchema ? (
+				p['items']['anyOf'] extends ReadonlyArray<Schema> ? UnionSchemaType<NonNullable<p['items']['anyOf']>>[] :
+				p['items']['oneOf'] extends ReadonlyArray<Schema> ? ArrayUnion<UnionSchemaType<NonNullable<p['items']['oneOf']>>> :
+				p['items']['allOf'] extends ReadonlyArray<Schema> ? UnionToIntersection<UnionSchemaType<NonNullable<p['items']['allOf']>>>[] :
+				never
+			) :
+				p['prefixItems'] extends ReadonlyArray<Schema> ? (
+					p['items'] extends NonNullable<Schema> ? [...ArrayToTuple<p['prefixItems']>, ...SchemaType<p['items']>[]] :
+					p['items'] extends false ? ArrayToTuple<p['prefixItems']> :
+					p['unevaluatedItems'] extends false ? ArrayToTuple<p['prefixItems']> :
+					[...ArrayToTuple<p['prefixItems']>, ...unknown[]]
+				) :
+					p['items'] extends NonNullable<Schema> ? SchemaType<p['items']>[] :
+					any[]
 		) :
-		p['items'] extends NonNullable<Schema> ? SchemaType<p['items']>[] :
-		any[]
-	) :
-	p['anyOf'] extends ReadonlyArray<Schema> ? UnionSchemaType<p['anyOf']> & PartialIntersection<UnionSchemaType<p['anyOf']>> :
-	p['oneOf'] extends ReadonlyArray<Schema> ? UnionSchemaType<p['oneOf']> :
-	any;
+			p['anyOf'] extends ReadonlyArray<Schema> ? UnionSchemaType<p['anyOf']> & PartialIntersection<UnionSchemaType<p['anyOf']>> :
+			p['oneOf'] extends ReadonlyArray<Schema> ? UnionSchemaType<p['oneOf']> :
+			any;
 
 export type SchemaType<p extends Schema> = NullOrUndefined<p, SchemaTypeDef<p>>;
diff --git a/packages/backend/src/models/ChatApproval.ts b/packages/backend/src/models/ChatApproval.ts
new file mode 100644
index 0000000000..55c9f07e9a
--- /dev/null
+++ b/packages/backend/src/models/ChatApproval.ts
@@ -0,0 +1,39 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { PrimaryColumn, Entity, Index, JoinColumn, Column, ManyToOne } from 'typeorm';
+import { id } from './util/id.js';
+import { MiUser } from './User.js';
+
+@Entity('chat_approval')
+@Index(['userId', 'otherId'], { unique: true })
+export class MiChatApproval {
+	@PrimaryColumn(id())
+	public id: string;
+
+	@Index()
+	@Column({
+		...id(),
+	})
+	public userId: MiUser['id'];
+
+	@ManyToOne(type => MiUser, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public user: MiUser | null;
+
+	@Index()
+	@Column({
+		...id(),
+	})
+	public otherId: MiUser['id'];
+
+	@ManyToOne(type => MiUser, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public other: MiUser | null;
+}
diff --git a/packages/backend/src/models/ChatMessage.ts b/packages/backend/src/models/ChatMessage.ts
new file mode 100644
index 0000000000..3d2b64268e
--- /dev/null
+++ b/packages/backend/src/models/ChatMessage.ts
@@ -0,0 +1,85 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { PrimaryColumn, Entity, Index, JoinColumn, Column, ManyToOne } from 'typeorm';
+import { id } from './util/id.js';
+import { MiUser } from './User.js';
+import { MiDriveFile } from './DriveFile.js';
+import { MiChatRoom } from './ChatRoom.js';
+
+@Entity('chat_message')
+export class MiChatMessage {
+	@PrimaryColumn(id())
+	public id: string;
+
+	@Index()
+	@Column({
+		...id(),
+	})
+	public fromUserId: MiUser['id'];
+
+	@ManyToOne(type => MiUser, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public fromUser: MiUser | null;
+
+	@Index()
+	@Column({
+		...id(), nullable: true,
+	})
+	public toUserId: MiUser['id'] | null;
+
+	@ManyToOne(type => MiUser, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public toUser: MiUser | null;
+
+	@Index()
+	@Column({
+		...id(), nullable: true,
+	})
+	public toRoomId: MiChatRoom['id'] | null;
+
+	@ManyToOne(type => MiChatRoom, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public toRoom: MiChatRoom | null;
+
+	@Column('varchar', {
+		length: 4096, nullable: true,
+	})
+	public text: string | null;
+
+	@Column('varchar', {
+		length: 512, nullable: true,
+	})
+	public uri: string | null;
+
+	@Column({
+		...id(),
+		array: true, default: '{}',
+	})
+	public reads: MiUser['id'][];
+
+	@Column({
+		...id(),
+		nullable: true,
+	})
+	public fileId: MiDriveFile['id'] | null;
+
+	@ManyToOne(type => MiDriveFile, {
+		onDelete: 'SET NULL',
+	})
+	@JoinColumn()
+	public file: MiDriveFile | null;
+
+	@Column('varchar', {
+		length: 1024, array: true, default: '{}',
+	})
+	public reactions: string[];
+}
diff --git a/packages/backend/src/models/ChatRoom.ts b/packages/backend/src/models/ChatRoom.ts
new file mode 100644
index 0000000000..ad2a910b78
--- /dev/null
+++ b/packages/backend/src/models/ChatRoom.ts
@@ -0,0 +1,41 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { PrimaryColumn, Entity, Index, JoinColumn, Column, ManyToOne } from 'typeorm';
+import { id } from './util/id.js';
+import { MiUser } from './User.js';
+
+@Entity('chat_room')
+export class MiChatRoom {
+	@PrimaryColumn(id())
+	public id: string;
+
+	@Column('varchar', {
+		length: 256,
+	})
+	public name: string;
+
+	@Index()
+	@Column({
+		...id(),
+	})
+	public ownerId: MiUser['id'];
+
+	@ManyToOne(type => MiUser, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public owner: MiUser | null;
+
+	@Column('varchar', {
+		length: 2048, default: '',
+	})
+	public description: string;
+
+	@Column('boolean', {
+		default: false,
+	})
+	public isArchived: boolean;
+}
diff --git a/packages/backend/src/models/ChatRoomInvitation.ts b/packages/backend/src/models/ChatRoomInvitation.ts
new file mode 100644
index 0000000000..36ce12bc92
--- /dev/null
+++ b/packages/backend/src/models/ChatRoomInvitation.ts
@@ -0,0 +1,45 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { PrimaryColumn, Entity, Index, JoinColumn, Column, ManyToOne } from 'typeorm';
+import { id } from './util/id.js';
+import { MiUser } from './User.js';
+import { MiChatRoom } from './ChatRoom.js';
+
+@Entity('chat_room_invitation')
+@Index(['userId', 'roomId'], { unique: true })
+export class MiChatRoomInvitation {
+	@PrimaryColumn(id())
+	public id: string;
+
+	@Index()
+	@Column({
+		...id(),
+	})
+	public userId: MiUser['id'];
+
+	@ManyToOne(type => MiUser, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public user: MiUser | null;
+
+	@Index()
+	@Column({
+		...id(),
+	})
+	public roomId: MiChatRoom['id'];
+
+	@ManyToOne(type => MiChatRoom, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public room: MiChatRoom | null;
+
+	@Column('boolean', {
+		default: false,
+	})
+	public ignored: boolean;
+}
diff --git a/packages/backend/src/models/ChatRoomMembership.ts b/packages/backend/src/models/ChatRoomMembership.ts
new file mode 100644
index 0000000000..3cb5524859
--- /dev/null
+++ b/packages/backend/src/models/ChatRoomMembership.ts
@@ -0,0 +1,45 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { PrimaryColumn, Entity, Index, JoinColumn, Column, ManyToOne } from 'typeorm';
+import { id } from './util/id.js';
+import { MiUser } from './User.js';
+import { MiChatRoom } from './ChatRoom.js';
+
+@Entity('chat_room_membership')
+@Index(['userId', 'roomId'], { unique: true })
+export class MiChatRoomMembership {
+	@PrimaryColumn(id())
+	public id: string;
+
+	@Index()
+	@Column({
+		...id(),
+	})
+	public userId: MiUser['id'];
+
+	@ManyToOne(type => MiUser, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public user: MiUser | null;
+
+	@Index()
+	@Column({
+		...id(),
+	})
+	public roomId: MiChatRoom['id'];
+
+	@ManyToOne(type => MiChatRoom, {
+		onDelete: 'CASCADE',
+	})
+	@JoinColumn()
+	public room: MiChatRoom | null;
+
+	@Column('boolean', {
+		default: false,
+	})
+	public isMuted: boolean;
+}
diff --git a/packages/backend/src/models/NoteUnread.ts b/packages/backend/src/models/NoteUnread.ts
deleted file mode 100644
index c759181117..0000000000
--- a/packages/backend/src/models/NoteUnread.ts
+++ /dev/null
@@ -1,68 +0,0 @@
-/*
- * SPDX-FileCopyrightText: syuilo and misskey-project
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-
-import { PrimaryColumn, Entity, Index, JoinColumn, Column, ManyToOne } from 'typeorm';
-import { id } from './util/id.js';
-import { MiUser } from './User.js';
-import { MiNote } from './Note.js';
-import type { MiChannel } from './Channel.js';
-
-@Entity('note_unread')
-@Index(['userId', 'noteId'], { unique: true })
-export class MiNoteUnread {
-	@PrimaryColumn(id())
-	public id: string;
-
-	@Index()
-	@Column(id())
-	public userId: MiUser['id'];
-
-	@ManyToOne(type => MiUser, {
-		onDelete: 'CASCADE',
-	})
-	@JoinColumn()
-	public user: MiUser | null;
-
-	@Index()
-	@Column(id())
-	public noteId: MiNote['id'];
-
-	@ManyToOne(type => MiNote, {
-		onDelete: 'CASCADE',
-	})
-	@JoinColumn()
-	public note: MiNote | null;
-
-	/**
-	 * メンションか否か
-	 */
-	@Index()
-	@Column('boolean')
-	public isMentioned: boolean;
-
-	/**
-	 * ダイレクト投稿か否か
-	 */
-	@Index()
-	@Column('boolean')
-	public isSpecified: boolean;
-
-	//#region Denormalized fields
-	@Index()
-	@Column({
-		...id(),
-		comment: '[Denormalized]',
-	})
-	public noteUserId: MiUser['id'];
-
-	@Index()
-	@Column({
-		...id(),
-		nullable: true,
-		comment: '[Denormalized]',
-	})
-	public noteChannelId: MiChannel['id'] | null;
-	//#endregion
-}
diff --git a/packages/backend/src/models/RepositoryModule.ts b/packages/backend/src/models/RepositoryModule.ts
index 04a9df6cfb..b7142d91bf 100644
--- a/packages/backend/src/models/RepositoryModule.ts
+++ b/packages/backend/src/models/RepositoryModule.ts
@@ -42,7 +42,6 @@ import {
 	MiNoteFavorite,
 	MiNoteReaction,
 	MiNoteThreadMuting,
-	MiNoteUnread,
 	MiPage,
 	MiPageLike,
 	MiPasswordResetRequest,
@@ -78,6 +77,11 @@ import {
 	MiUserPublickey,
 	MiUserSecurityKey,
 	MiWebhook,
+	MiChatMessage,
+	MiChatRoom,
+	MiChatRoomMembership,
+	MiChatRoomInvitation,
+	MiChatApproval,
 } from './_.js';
 import type { Provider } from '@nestjs/common';
 import type { DataSource } from 'typeorm';
@@ -136,12 +140,6 @@ const $noteReactionsRepository: Provider = {
 	inject: [DI.db],
 };
 
-const $noteUnreadsRepository: Provider = {
-	provide: DI.noteUnreadsRepository,
-	useFactory: (db: DataSource) => db.getRepository(MiNoteUnread).extend(miRepository as MiRepository<MiNoteUnread>),
-	inject: [DI.db],
-};
-
 const $pollsRepository: Provider = {
 	provide: DI.pollsRepository,
 	useFactory: (db: DataSource) => db.getRepository(MiPoll).extend(miRepository as MiRepository<MiPoll>),
@@ -288,7 +286,7 @@ const $swSubscriptionsRepository: Provider = {
 
 const $systemAccountsRepository: Provider = {
 	provide: DI.systemAccountsRepository,
-	useFactory: (db: DataSource) => db.getRepository(MiSystemAccount),
+	useFactory: (db: DataSource) => db.getRepository(MiSystemAccount).extend(miRepository as MiRepository<MiSystemAccount>),
 	inject: [DI.db],
 };
 
@@ -306,7 +304,7 @@ const $abuseUserReportsRepository: Provider = {
 
 const $abuseReportNotificationRecipientRepository: Provider = {
 	provide: DI.abuseReportNotificationRecipientRepository,
-	useFactory: (db: DataSource) => db.getRepository(MiAbuseReportNotificationRecipient),
+	useFactory: (db: DataSource) => db.getRepository(MiAbuseReportNotificationRecipient).extend(miRepository as MiRepository<MiAbuseReportNotificationRecipient>),
 	inject: [DI.db],
 };
 
@@ -438,7 +436,7 @@ const $webhooksRepository: Provider = {
 
 const $systemWebhooksRepository: Provider = {
 	provide: DI.systemWebhooksRepository,
-	useFactory: (db: DataSource) => db.getRepository(MiSystemWebhook),
+	useFactory: (db: DataSource) => db.getRepository(MiSystemWebhook).extend(miRepository as MiRepository<MiSystemWebhook>),
 	inject: [DI.db],
 };
 
@@ -490,6 +488,36 @@ const $userMemosRepository: Provider = {
 	inject: [DI.db],
 };
 
+const $chatMessagesRepository: Provider = {
+	provide: DI.chatMessagesRepository,
+	useFactory: (db: DataSource) => db.getRepository(MiChatMessage).extend(miRepository as MiRepository<MiChatMessage>),
+	inject: [DI.db],
+};
+
+const $chatRoomsRepository: Provider = {
+	provide: DI.chatRoomsRepository,
+	useFactory: (db: DataSource) => db.getRepository(MiChatRoom).extend(miRepository as MiRepository<MiChatRoom>),
+	inject: [DI.db],
+};
+
+const $chatRoomMembershipsRepository: Provider = {
+	provide: DI.chatRoomMembershipsRepository,
+	useFactory: (db: DataSource) => db.getRepository(MiChatRoomMembership).extend(miRepository as MiRepository<MiChatRoomMembership>),
+	inject: [DI.db],
+};
+
+const $chatRoomInvitationsRepository: Provider = {
+	provide: DI.chatRoomInvitationsRepository,
+	useFactory: (db: DataSource) => db.getRepository(MiChatRoomInvitation).extend(miRepository as MiRepository<MiChatRoomInvitation>),
+	inject: [DI.db],
+};
+
+const $chatApprovalsRepository: Provider = {
+	provide: DI.chatApprovalsRepository,
+	useFactory: (db: DataSource) => db.getRepository(MiChatApproval).extend(miRepository as MiRepository<MiChatApproval>),
+	inject: [DI.db],
+};
+
 const $bubbleGameRecordsRepository: Provider = {
 	provide: DI.bubbleGameRecordsRepository,
 	useFactory: (db: DataSource) => db.getRepository(MiBubbleGameRecord).extend(miRepository as MiRepository<MiBubbleGameRecord>),
@@ -514,7 +542,6 @@ const $reversiGamesRepository: Provider = {
 		$noteFavoritesRepository,
 		$noteThreadMutingsRepository,
 		$noteReactionsRepository,
-		$noteUnreadsRepository,
 		$pollsRepository,
 		$pollVotesRepository,
 		$userProfilesRepository,
@@ -573,6 +600,11 @@ const $reversiGamesRepository: Provider = {
 		$flashsRepository,
 		$flashLikesRepository,
 		$userMemosRepository,
+		$chatMessagesRepository,
+		$chatRoomsRepository,
+		$chatRoomMembershipsRepository,
+		$chatRoomInvitationsRepository,
+		$chatApprovalsRepository,
 		$bubbleGameRecordsRepository,
 		$reversiGamesRepository,
 	],
@@ -586,7 +618,6 @@ const $reversiGamesRepository: Provider = {
 		$noteFavoritesRepository,
 		$noteThreadMutingsRepository,
 		$noteReactionsRepository,
-		$noteUnreadsRepository,
 		$pollsRepository,
 		$pollVotesRepository,
 		$userProfilesRepository,
@@ -645,6 +676,11 @@ const $reversiGamesRepository: Provider = {
 		$flashsRepository,
 		$flashLikesRepository,
 		$userMemosRepository,
+		$chatMessagesRepository,
+		$chatRoomsRepository,
+		$chatRoomMembershipsRepository,
+		$chatRoomInvitationsRepository,
+		$chatApprovalsRepository,
 		$bubbleGameRecordsRepository,
 		$reversiGamesRepository,
 	],
diff --git a/packages/backend/src/models/User.ts b/packages/backend/src/models/User.ts
index 630240efde..bc652cea62 100644
--- a/packages/backend/src/models/User.ts
+++ b/packages/backend/src/models/User.ts
@@ -225,6 +225,17 @@ export class MiUser {
 	})
 	public emojis: string[];
 
+	// チャットを許可する相手
+	// everyone: 誰からでも
+	// followers: フォロワーのみ
+	// following: フォローしているユーザーのみ
+	// mutual: 相互フォローのみ
+	// none: 誰からも受け付けない
+	@Column('varchar', {
+		length: 128, default: 'mutual',
+	})
+	public chatScope: 'everyone' | 'followers' | 'following' | 'mutual' | 'none';
+
 	@Index()
 	@Column('varchar', {
 		length: 128, nullable: true,
diff --git a/packages/backend/src/models/_.ts b/packages/backend/src/models/_.ts
index fa15760c00..e852b302f3 100644
--- a/packages/backend/src/models/_.ts
+++ b/packages/backend/src/models/_.ts
@@ -3,13 +3,10 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import { FindOneOptions, InsertQueryBuilder, ObjectLiteral, Repository, SelectQueryBuilder, TypeORMError } from 'typeorm';
-import { DriverUtils } from 'typeorm/driver/DriverUtils.js';
+import { FindOneOptions, InsertQueryBuilder, ObjectLiteral, Repository, SelectQueryBuilder } from 'typeorm';
 import { RelationCountLoader } from 'typeorm/query-builder/relation-count/RelationCountLoader.js';
 import { RelationIdLoader } from 'typeorm/query-builder/relation-id/RelationIdLoader.js';
 import { RawSqlResultsToEntityTransformer } from 'typeorm/query-builder/transformer/RawSqlResultsToEntityTransformer.js';
-import { ObjectUtils } from 'typeorm/util/ObjectUtils.js';
-import { OrmUtils } from 'typeorm/util/OrmUtils.js';
 import { MiAbuseUserReport } from '@/models/AbuseUserReport.js';
 import { MiAbuseReportNotificationRecipient } from '@/models/AbuseReportNotificationRecipient.js';
 import { MiAccessToken } from '@/models/AccessToken.js';
@@ -43,7 +40,6 @@ import { MiNote } from '@/models/Note.js';
 import { MiNoteFavorite } from '@/models/NoteFavorite.js';
 import { MiNoteReaction } from '@/models/NoteReaction.js';
 import { MiNoteThreadMuting } from '@/models/NoteThreadMuting.js';
-import { MiNoteUnread } from '@/models/NoteUnread.js';
 import { MiPage } from '@/models/Page.js';
 import { MiPageLike } from '@/models/PageLike.js';
 import { MiPasswordResetRequest } from '@/models/PasswordResetRequest.js';
@@ -78,6 +74,11 @@ import { MiRoleAssignment } from '@/models/RoleAssignment.js';
 import { MiFlash } from '@/models/Flash.js';
 import { MiFlashLike } from '@/models/FlashLike.js';
 import { MiUserListFavorite } from '@/models/UserListFavorite.js';
+import { MiChatMessage } from '@/models/ChatMessage.js';
+import { MiChatRoom } from '@/models/ChatRoom.js';
+import { MiChatRoomMembership } from '@/models/ChatRoomMembership.js';
+import { MiChatRoomInvitation } from '@/models/ChatRoomInvitation.js';
+import { MiChatApproval } from '@/models/ChatApproval.js';
 import { MiBubbleGameRecord } from '@/models/BubbleGameRecord.js';
 import { MiReversiGame } from '@/models/ReversiGame.js';
 import type { QueryDeepPartialEntity } from 'typeorm/query-builder/QueryPartialEntity.js';
@@ -159,7 +160,6 @@ export {
 	MiNoteFavorite,
 	MiNoteReaction,
 	MiNoteThreadMuting,
-	MiNoteUnread,
 	MiPage,
 	MiPageLike,
 	MiPasswordResetRequest,
@@ -194,6 +194,11 @@ export {
 	MiFlash,
 	MiFlashLike,
 	MiUserMemo,
+	MiChatMessage,
+	MiChatRoom,
+	MiChatRoomMembership,
+	MiChatRoomInvitation,
+	MiChatApproval,
 	MiBubbleGameRecord,
 	MiReversiGame,
 };
@@ -231,7 +236,6 @@ export type NotesRepository = Repository<MiNote> & MiRepository<MiNote>;
 export type NoteFavoritesRepository = Repository<MiNoteFavorite> & MiRepository<MiNoteFavorite>;
 export type NoteReactionsRepository = Repository<MiNoteReaction> & MiRepository<MiNoteReaction>;
 export type NoteThreadMutingsRepository = Repository<MiNoteThreadMuting> & MiRepository<MiNoteThreadMuting>;
-export type NoteUnreadsRepository = Repository<MiNoteUnread> & MiRepository<MiNoteUnread>;
 export type PagesRepository = Repository<MiPage> & MiRepository<MiPage>;
 export type PageLikesRepository = Repository<MiPageLike> & MiRepository<MiPageLike>;
 export type PasswordResetRequestsRepository = Repository<MiPasswordResetRequest> & MiRepository<MiPasswordResetRequest>;
@@ -266,5 +270,10 @@ export type RoleAssignmentsRepository = Repository<MiRoleAssignment> & MiReposit
 export type FlashsRepository = Repository<MiFlash> & MiRepository<MiFlash>;
 export type FlashLikesRepository = Repository<MiFlashLike> & MiRepository<MiFlashLike>;
 export type UserMemoRepository = Repository<MiUserMemo> & MiRepository<MiUserMemo>;
+export type ChatMessagesRepository = Repository<MiChatMessage> & MiRepository<MiChatMessage>;
+export type ChatRoomsRepository = Repository<MiChatRoom> & MiRepository<MiChatRoom>;
+export type ChatRoomMembershipsRepository = Repository<MiChatRoomMembership> & MiRepository<MiChatRoomMembership>;
+export type ChatRoomInvitationsRepository = Repository<MiChatRoomInvitation> & MiRepository<MiChatRoomInvitation>;
+export type ChatApprovalsRepository = Repository<MiChatApproval> & MiRepository<MiChatApproval>;
 export type BubbleGameRecordsRepository = Repository<MiBubbleGameRecord> & MiRepository<MiBubbleGameRecord>;
 export type ReversiGamesRepository = Repository<MiReversiGame> & MiRepository<MiReversiGame>;
diff --git a/packages/backend/src/models/json-schema/chat-message.ts b/packages/backend/src/models/json-schema/chat-message.ts
new file mode 100644
index 0000000000..44b7298702
--- /dev/null
+++ b/packages/backend/src/models/json-schema/chat-message.ts
@@ -0,0 +1,146 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+export const packedChatMessageSchema = {
+	type: 'object',
+	properties: {
+		id: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		createdAt: {
+			type: 'string',
+			format: 'date-time',
+			optional: false, nullable: false,
+		},
+		fromUserId: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		fromUser: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'UserLite',
+		},
+		toUserId: {
+			type: 'string',
+			optional: true, nullable: true,
+		},
+		toUser: {
+			type: 'object',
+			optional: true, nullable: true,
+			ref: 'UserLite',
+		},
+		toRoomId: {
+			type: 'string',
+			optional: true, nullable: true,
+		},
+		toRoom: {
+			type: 'object',
+			optional: true, nullable: true,
+			ref: 'ChatRoom',
+		},
+		text: {
+			type: 'string',
+			optional: true, nullable: true,
+		},
+		fileId: {
+			type: 'string',
+			optional: true, nullable: true,
+		},
+		file: {
+			type: 'object',
+			optional: true, nullable: true,
+			ref: 'DriveFile',
+		},
+		isRead: {
+			type: 'boolean',
+			optional: true, nullable: false,
+		},
+		reactions: {
+			type: 'array',
+			optional: false, nullable: false,
+			items: {
+				type: 'object',
+				optional: false, nullable: false,
+				properties: {
+					reaction: {
+						type: 'string',
+						optional: false, nullable: false,
+					},
+					user: {
+						type: 'object',
+						optional: true, nullable: true,
+						ref: 'UserLite',
+					},
+				},
+			},
+		},
+	},
+} as const;
+
+export const packedChatMessageLiteSchema = {
+	type: 'object',
+	properties: {
+		id: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		createdAt: {
+			type: 'string',
+			format: 'date-time',
+			optional: false, nullable: false,
+		},
+		fromUserId: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		fromUser: {
+			type: 'object',
+			optional: true, nullable: false,
+			ref: 'UserLite',
+		},
+		toUserId: {
+			type: 'string',
+			optional: true, nullable: true,
+		},
+		toRoomId: {
+			type: 'string',
+			optional: true, nullable: true,
+		},
+		text: {
+			type: 'string',
+			optional: true, nullable: true,
+		},
+		fileId: {
+			type: 'string',
+			optional: true, nullable: true,
+		},
+		file: {
+			type: 'object',
+			optional: true, nullable: true,
+			ref: 'DriveFile',
+		},
+		reactions: {
+			type: 'array',
+			optional: false, nullable: false,
+			items: {
+				type: 'object',
+				optional: false, nullable: false,
+				properties: {
+					reaction: {
+						type: 'string',
+						optional: false, nullable: false,
+					},
+					user: {
+						type: 'object',
+						optional: true, nullable: true,
+						ref: 'UserLite',
+					},
+				},
+			},
+		},
+	},
+} as const;
diff --git a/packages/backend/src/models/json-schema/chat-room-invitation.ts b/packages/backend/src/models/json-schema/chat-room-invitation.ts
new file mode 100644
index 0000000000..204c959b2c
--- /dev/null
+++ b/packages/backend/src/models/json-schema/chat-room-invitation.ts
@@ -0,0 +1,37 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+export const packedChatRoomInvitationSchema = {
+	type: 'object',
+	properties: {
+		id: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		createdAt: {
+			type: 'string',
+			format: 'date-time',
+			optional: false, nullable: false,
+		},
+		userId: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		user: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'UserLite',
+		},
+		roomId: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		room: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'ChatRoom',
+		},
+	},
+} as const;
diff --git a/packages/backend/src/models/json-schema/chat-room-membership.ts b/packages/backend/src/models/json-schema/chat-room-membership.ts
new file mode 100644
index 0000000000..adb73f9dde
--- /dev/null
+++ b/packages/backend/src/models/json-schema/chat-room-membership.ts
@@ -0,0 +1,37 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+export const packedChatRoomMembershipSchema = {
+	type: 'object',
+	properties: {
+		id: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		createdAt: {
+			type: 'string',
+			format: 'date-time',
+			optional: false, nullable: false,
+		},
+		userId: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		user: {
+			type: 'object',
+			optional: true, nullable: false,
+			ref: 'UserLite',
+		},
+		roomId: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		room: {
+			type: 'object',
+			optional: true, nullable: false,
+			ref: 'ChatRoom',
+		},
+	},
+} as const;
diff --git a/packages/backend/src/models/json-schema/chat-room.ts b/packages/backend/src/models/json-schema/chat-room.ts
new file mode 100644
index 0000000000..e97556e378
--- /dev/null
+++ b/packages/backend/src/models/json-schema/chat-room.ts
@@ -0,0 +1,40 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+export const packedChatRoomSchema = {
+	type: 'object',
+	properties: {
+		id: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		createdAt: {
+			type: 'string',
+			format: 'date-time',
+			optional: false, nullable: false,
+		},
+		ownerId: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		owner: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'UserLite',
+		},
+		name: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		description: {
+			type: 'string',
+			optional: false, nullable: false,
+		},
+		isMuted: {
+			type: 'boolean',
+			optional: true, nullable: false,
+		},
+	},
+} as const;
diff --git a/packages/backend/src/models/json-schema/role.ts b/packages/backend/src/models/json-schema/role.ts
index 3537de94c8..1685a806c9 100644
--- a/packages/backend/src/models/json-schema/role.ts
+++ b/packages/backend/src/models/json-schema/role.ts
@@ -292,6 +292,10 @@ export const packedRolePoliciesSchema = {
 			type: 'boolean',
 			optional: false, nullable: false,
 		},
+		canChat: {
+			type: 'boolean',
+			optional: false, nullable: false,
+		},
 	},
 } as const;
 
diff --git a/packages/backend/src/models/json-schema/user.ts b/packages/backend/src/models/json-schema/user.ts
index 38631f907d..b10430782b 100644
--- a/packages/backend/src/models/json-schema/user.ts
+++ b/packages/backend/src/models/json-schema/user.ts
@@ -358,6 +358,11 @@ export const packedUserDetailedNotMeOnlySchema = {
 			nullable: false, optional: false,
 			enum: ['public', 'followers', 'private'],
 		},
+		chatScope: {
+			type: 'string',
+			nullable: false, optional: false,
+			enum: ['everyone', 'following', 'followers', 'mutual', 'none'],
+		},
 		roles: {
 			type: 'array',
 			nullable: false, optional: false,
@@ -540,6 +545,10 @@ export const packedMeDetailedOnlySchema = {
 			type: 'boolean',
 			nullable: false, optional: false,
 		},
+		hasUnreadChatMessages: {
+			type: 'boolean',
+			nullable: false, optional: false,
+		},
 		hasUnreadNotification: {
 			type: 'boolean',
 			nullable: false, optional: false,
diff --git a/packages/backend/src/postgres.ts b/packages/backend/src/postgres.ts
index 043332d4b5..4694e7003d 100644
--- a/packages/backend/src/postgres.ts
+++ b/packages/backend/src/postgres.ts
@@ -8,6 +8,9 @@ import pg from 'pg';
 import { DataSource, Logger } from 'typeorm';
 import * as highlight from 'cli-highlight';
 import { entities as charts } from '@/core/chart/entities.js';
+import { Config } from '@/config.js';
+import MisskeyLogger from '@/logger.js';
+import { bindThis } from '@/decorators.js';
 
 import { MiAbuseUserReport } from '@/models/AbuseUserReport.js';
 import { MiAbuseReportNotificationRecipient } from '@/models/AbuseReportNotificationRecipient.js';
@@ -42,7 +45,6 @@ import { MiNote } from '@/models/Note.js';
 import { MiNoteFavorite } from '@/models/NoteFavorite.js';
 import { MiNoteReaction } from '@/models/NoteReaction.js';
 import { MiNoteThreadMuting } from '@/models/NoteThreadMuting.js';
-import { MiNoteUnread } from '@/models/NoteUnread.js';
 import { MiPage } from '@/models/Page.js';
 import { MiPageLike } from '@/models/PageLike.js';
 import { MiPasswordResetRequest } from '@/models/PasswordResetRequest.js';
@@ -76,13 +78,14 @@ import { MiRoleAssignment } from '@/models/RoleAssignment.js';
 import { MiFlash } from '@/models/Flash.js';
 import { MiFlashLike } from '@/models/FlashLike.js';
 import { MiUserMemo } from '@/models/UserMemo.js';
+import { MiChatMessage } from '@/models/ChatMessage.js';
+import { MiChatRoom } from '@/models/ChatRoom.js';
+import { MiChatRoomMembership } from '@/models/ChatRoomMembership.js';
+import { MiChatRoomInvitation } from '@/models/ChatRoomInvitation.js';
 import { MiBubbleGameRecord } from '@/models/BubbleGameRecord.js';
 import { MiReversiGame } from '@/models/ReversiGame.js';
-
-import { Config } from '@/config.js';
-import MisskeyLogger from '@/logger.js';
-import { bindThis } from '@/decorators.js';
-import { MiSystemAccount } from './models/SystemAccount.js';
+import { MiChatApproval } from '@/models/ChatApproval.js';
+import { MiSystemAccount } from '@/models/SystemAccount.js';
 
 pg.types.setTypeParser(20, Number);
 
@@ -195,7 +198,6 @@ export const entities = [
 	MiNoteFavorite,
 	MiNoteReaction,
 	MiNoteThreadMuting,
-	MiNoteUnread,
 	MiPage,
 	MiPageLike,
 	MiGalleryPost,
@@ -236,6 +238,11 @@ export const entities = [
 	MiFlash,
 	MiFlashLike,
 	MiUserMemo,
+	MiChatMessage,
+	MiChatRoom,
+	MiChatRoomMembership,
+	MiChatRoomInvitation,
+	MiChatApproval,
 	MiBubbleGameRecord,
 	MiReversiGame,
 	...charts,
diff --git a/packages/backend/src/server/ServerModule.ts b/packages/backend/src/server/ServerModule.ts
index 3ab0b815f2..0223650329 100644
--- a/packages/backend/src/server/ServerModule.ts
+++ b/packages/backend/src/server/ServerModule.ts
@@ -44,6 +44,8 @@ import { QueueStatsChannelService } from './api/stream/channels/queue-stats.js';
 import { ServerStatsChannelService } from './api/stream/channels/server-stats.js';
 import { UserListChannelService } from './api/stream/channels/user-list.js';
 import { RoleTimelineChannelService } from './api/stream/channels/role-timeline.js';
+import { ChatUserChannelService } from './api/stream/channels/chat-user.js';
+import { ChatRoomChannelService } from './api/stream/channels/chat-room.js';
 import { ReversiChannelService } from './api/stream/channels/reversi.js';
 import { ReversiGameChannelService } from './api/stream/channels/reversi-game.js';
 import { SigninWithPasskeyApiService } from './api/SigninWithPasskeyApiService.js';
@@ -84,6 +86,8 @@ import { SigninWithPasskeyApiService } from './api/SigninWithPasskeyApiService.j
 		GlobalTimelineChannelService,
 		HashtagChannelService,
 		RoleTimelineChannelService,
+		ChatUserChannelService,
+		ChatRoomChannelService,
 		ReversiChannelService,
 		ReversiGameChannelService,
 		HomeTimelineChannelService,
diff --git a/packages/backend/src/server/api/StreamingApiServerService.ts b/packages/backend/src/server/api/StreamingApiServerService.ts
index b8f448477b..2a4e1fc574 100644
--- a/packages/backend/src/server/api/StreamingApiServerService.ts
+++ b/packages/backend/src/server/api/StreamingApiServerService.ts
@@ -9,7 +9,6 @@ import * as Redis from 'ioredis';
 import * as WebSocket from 'ws';
 import { DI } from '@/di-symbols.js';
 import type { UsersRepository, MiAccessToken } from '@/models/_.js';
-import { NoteReadService } from '@/core/NoteReadService.js';
 import { NotificationService } from '@/core/NotificationService.js';
 import { bindThis } from '@/decorators.js';
 import { CacheService } from '@/core/CacheService.js';
@@ -35,7 +34,6 @@ export class StreamingApiServerService {
 		private usersRepository: UsersRepository,
 
 		private cacheService: CacheService,
-		private noteReadService: NoteReadService,
 		private authenticateService: AuthenticateService,
 		private channelsService: ChannelsService,
 		private notificationService: NotificationService,
@@ -96,7 +94,6 @@ export class StreamingApiServerService {
 
 			const stream = new MainStreamConnection(
 				this.channelsService,
-				this.noteReadService,
 				this.notificationService,
 				this.cacheService,
 				this.channelFollowingService,
diff --git a/packages/backend/src/server/api/endpoint-list.ts b/packages/backend/src/server/api/endpoint-list.ts
index 560d3f6587..9bb29e138b 100644
--- a/packages/backend/src/server/api/endpoint-list.ts
+++ b/packages/backend/src/server/api/endpoint-list.ts
@@ -263,7 +263,6 @@ export * as 'i/notifications-grouped' from './endpoints/i/notifications-grouped.
 export * as 'i/page-likes' from './endpoints/i/page-likes.js';
 export * as 'i/pages' from './endpoints/i/pages.js';
 export * as 'i/pin' from './endpoints/i/pin.js';
-export * as 'i/read-all-unread-notes' from './endpoints/i/read-all-unread-notes.js';
 export * as 'i/read-announcement' from './endpoints/i/read-announcement.js';
 export * as 'i/regenerate-token' from './endpoints/i/regenerate-token.js';
 export * as 'i/registry/get' from './endpoints/i/registry/get.js';
@@ -397,4 +396,26 @@ export * as 'users/search' from './endpoints/users/search.js';
 export * as 'users/search-by-username-and-host' from './endpoints/users/search-by-username-and-host.js';
 export * as 'users/show' from './endpoints/users/show.js';
 export * as 'users/update-memo' from './endpoints/users/update-memo.js';
+export * as 'chat/messages/create-to-user' from './endpoints/chat/messages/create-to-user.js';
+export * as 'chat/messages/create-to-room' from './endpoints/chat/messages/create-to-room.js';
+export * as 'chat/messages/delete' from './endpoints/chat/messages/delete.js';
+export * as 'chat/messages/show' from './endpoints/chat/messages/show.js';
+export * as 'chat/messages/react' from './endpoints/chat/messages/react.js';
+export * as 'chat/messages/user-timeline' from './endpoints/chat/messages/user-timeline.js';
+export * as 'chat/messages/room-timeline' from './endpoints/chat/messages/room-timeline.js';
+export * as 'chat/messages/search' from './endpoints/chat/messages/search.js';
+export * as 'chat/rooms/create' from './endpoints/chat/rooms/create.js';
+export * as 'chat/rooms/delete' from './endpoints/chat/rooms/delete.js';
+export * as 'chat/rooms/join' from './endpoints/chat/rooms/join.js';
+export * as 'chat/rooms/leave' from './endpoints/chat/rooms/leave.js';
+export * as 'chat/rooms/mute' from './endpoints/chat/rooms/mute.js';
+export * as 'chat/rooms/show' from './endpoints/chat/rooms/show.js';
+export * as 'chat/rooms/owned' from './endpoints/chat/rooms/owned.js';
+export * as 'chat/rooms/joining' from './endpoints/chat/rooms/joining.js';
+export * as 'chat/rooms/update' from './endpoints/chat/rooms/update.js';
+export * as 'chat/rooms/members' from './endpoints/chat/rooms/members.js';
+export * as 'chat/rooms/invitations/create' from './endpoints/chat/rooms/invitations/create.js';
+export * as 'chat/rooms/invitations/ignore' from './endpoints/chat/rooms/invitations/ignore.js';
+export * as 'chat/rooms/invitations/inbox' from './endpoints/chat/rooms/invitations/inbox.js';
+export * as 'chat/history' from './endpoints/chat/history.js';
 export * as 'v2/admin/emoji/list' from './endpoints/v2/admin/emoji/list.js';
diff --git a/packages/backend/src/server/api/endpoints/antennas/notes.ts b/packages/backend/src/server/api/endpoints/antennas/notes.ts
index f4dfe1ecc4..727697ea14 100644
--- a/packages/backend/src/server/api/endpoints/antennas/notes.ts
+++ b/packages/backend/src/server/api/endpoints/antennas/notes.ts
@@ -8,7 +8,6 @@ import * as Redis from 'ioredis';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import type { NotesRepository, AntennasRepository } from '@/models/_.js';
 import { QueryService } from '@/core/QueryService.js';
-import { NoteReadService } from '@/core/NoteReadService.js';
 import { DI } from '@/di-symbols.js';
 import { NoteEntityService } from '@/core/entities/NoteEntityService.js';
 import { IdService } from '@/core/IdService.js';
@@ -59,9 +58,6 @@ export const paramDef = {
 @Injectable()
 export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
 	constructor(
-		@Inject(DI.redisForTimelines)
-		private redisForTimelines: Redis.Redis,
-
 		@Inject(DI.notesRepository)
 		private notesRepository: NotesRepository,
 
@@ -71,7 +67,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private idService: IdService,
 		private noteEntityService: NoteEntityService,
 		private queryService: QueryService,
-		private noteReadService: NoteReadService,
 		private fanoutTimelineService: FanoutTimelineService,
 		private globalEventService: GlobalEventService,
 	) {
@@ -124,8 +119,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				notes.sort((a, b) => a.id > b.id ? -1 : 1);
 			}
 
-			this.noteReadService.read(me.id, notes);
-
 			return await this.noteEntityService.packMany(notes, me);
 		});
 	}
diff --git a/packages/backend/src/server/api/endpoints/chat/history.ts b/packages/backend/src/server/api/endpoints/chat/history.ts
new file mode 100644
index 0000000000..7553a751e0
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/history.ts
@@ -0,0 +1,73 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'read:chat',
+
+	res: {
+		type: 'array',
+		optional: false, nullable: false,
+		items: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'ChatMessage',
+		},
+	},
+
+	errors: {
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
+		room: { type: 'boolean', default: false },
+	},
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatEntityService: ChatEntityService,
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const history = ps.room ? await this.chatService.roomHistory(me.id, ps.limit) : await this.chatService.userHistory(me.id, ps.limit);
+
+			const packedMessages = await this.chatEntityService.packMessagesDetailed(history, me);
+
+			if (ps.room) {
+				const roomIds = history.map(m => m.toRoomId!);
+				const readStateMap = await this.chatService.getRoomReadStateMap(me.id, roomIds);
+
+				for (const message of packedMessages) {
+					message.isRead = readStateMap[message.toRoomId!] ?? false;
+				}
+			} else {
+				const otherIds = history.map(m => m.fromUserId === me.id ? m.toUserId! : m.fromUserId!);
+				const readStateMap = await this.chatService.getUserReadStateMap(me.id, otherIds);
+
+				for (const message of packedMessages) {
+					const otherId = message.fromUserId === me.id ? message.toUserId! : message.fromUserId!;
+					message.isRead = readStateMap[otherId] ?? false;
+				}
+			}
+
+			return packedMessages;
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/create-to-room.ts b/packages/backend/src/server/api/endpoints/chat/messages/create-to-room.ts
new file mode 100644
index 0000000000..1f334d5750
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/messages/create-to-room.ts
@@ -0,0 +1,105 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import ms from 'ms';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { GetterService } from '@/server/api/GetterService.js';
+import { DI } from '@/di-symbols.js';
+import { ApiError } from '@/server/api/error.js';
+import { ChatService } from '@/core/ChatService.js';
+import type { DriveFilesRepository, MiUser } from '@/models/_.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+	requiredRolePolicy: 'canChat',
+
+	prohibitMoved: true,
+
+	kind: 'write:chat',
+
+	limit: {
+		duration: ms('1hour'),
+		max: 500,
+	},
+
+	res: {
+		type: 'object',
+		optional: false, nullable: false,
+		ref: 'ChatMessageLite',
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: '8098520d-2da5-4e8f-8ee1-df78b55a4ec6',
+		},
+
+		noSuchFile: {
+			message: 'No such file.',
+			code: 'NO_SUCH_FILE',
+			id: 'b6accbd3-1d7b-4d9f-bdb7-eb185bac06db',
+		},
+
+		contentRequired: {
+			message: 'Content required. You need to set text or fileId.',
+			code: 'CONTENT_REQUIRED',
+			id: '340517b7-6d04-42c0-bac1-37ee804e3594',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		text: { type: 'string', nullable: true, maxLength: 2000 },
+		fileId: { type: 'string', format: 'misskey:id' },
+		toRoomId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['toRoomId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		@Inject(DI.driveFilesRepository)
+		private driveFilesRepository: DriveFilesRepository,
+
+		private getterService: GetterService,
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const room = await this.chatService.findRoomById(ps.toRoomId);
+			if (room == null) {
+				throw new ApiError(meta.errors.noSuchRoom);
+			}
+
+			let file = null;
+			if (ps.fileId != null) {
+				file = await this.driveFilesRepository.findOneBy({
+					id: ps.fileId,
+					userId: me.id,
+				});
+
+				if (file == null) {
+					throw new ApiError(meta.errors.noSuchFile);
+				}
+			}
+
+			// テキストが無いかつ添付ファイルも無かったらエラー
+			if (ps.text == null && file == null) {
+				throw new ApiError(meta.errors.contentRequired);
+			}
+
+			return await this.chatService.createMessageToRoom(me, room, {
+				text: ps.text,
+				file: file,
+			});
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/create-to-user.ts b/packages/backend/src/server/api/endpoints/chat/messages/create-to-user.ts
new file mode 100644
index 0000000000..6b77a026fb
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/messages/create-to-user.ts
@@ -0,0 +1,122 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import ms from 'ms';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { GetterService } from '@/server/api/GetterService.js';
+import { DI } from '@/di-symbols.js';
+import { ApiError } from '@/server/api/error.js';
+import { ChatService } from '@/core/ChatService.js';
+import type { DriveFilesRepository, MiUser } from '@/models/_.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+	requiredRolePolicy: 'canChat',
+
+	prohibitMoved: true,
+
+	kind: 'write:chat',
+
+	limit: {
+		duration: ms('1hour'),
+		max: 500,
+	},
+
+	res: {
+		type: 'object',
+		optional: false, nullable: false,
+		ref: 'ChatMessageLite',
+	},
+
+	errors: {
+		recipientIsYourself: {
+			message: 'You can not send a message to yourself.',
+			code: 'RECIPIENT_IS_YOURSELF',
+			id: '17e2ba79-e22a-4cbc-bf91-d327643f4a7e',
+		},
+
+		noSuchUser: {
+			message: 'No such user.',
+			code: 'NO_SUCH_USER',
+			id: '11795c64-40ea-4198-b06e-3c873ed9039d',
+		},
+
+		noSuchFile: {
+			message: 'No such file.',
+			code: 'NO_SUCH_FILE',
+			id: '4372b8e2-185d-4146-8749-2f68864a3e5f',
+		},
+
+		contentRequired: {
+			message: 'Content required. You need to set text or fileId.',
+			code: 'CONTENT_REQUIRED',
+			id: '25587321-b0e6-449c-9239-f8925092942c',
+		},
+
+		youHaveBeenBlocked: {
+			message: 'You cannot send a message because you have been blocked by this user.',
+			code: 'YOU_HAVE_BEEN_BLOCKED',
+			id: 'c15a5199-7422-4968-941a-2a462c478f7d',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		text: { type: 'string', nullable: true, maxLength: 2000 },
+		fileId: { type: 'string', format: 'misskey:id' },
+		toUserId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['toUserId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		@Inject(DI.driveFilesRepository)
+		private driveFilesRepository: DriveFilesRepository,
+
+		private getterService: GetterService,
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			let file = null;
+			if (ps.fileId != null) {
+				file = await this.driveFilesRepository.findOneBy({
+					id: ps.fileId,
+					userId: me.id,
+				});
+
+				if (file == null) {
+					throw new ApiError(meta.errors.noSuchFile);
+				}
+			}
+
+			// テキストが無いかつ添付ファイルも無かったらエラー
+			if (ps.text == null && file == null) {
+				throw new ApiError(meta.errors.contentRequired);
+			}
+
+			// Myself
+			if (ps.toUserId === me.id) {
+				throw new ApiError(meta.errors.recipientIsYourself);
+			}
+
+			const toUser = await this.getterService.getUser(ps.toUserId).catch(err => {
+				if (err.id === '15348ddd-432d-49c2-8a5a-8069753becff') throw new ApiError(meta.errors.noSuchUser);
+				throw err;
+			});
+
+			return await this.chatService.createMessageToUser(me, toUser, {
+				text: ps.text,
+				file: file,
+			});
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/delete.ts b/packages/backend/src/server/api/endpoints/chat/messages/delete.ts
new file mode 100644
index 0000000000..959599ddcf
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/messages/delete.ts
@@ -0,0 +1,52 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'write:chat',
+
+	res: {
+	},
+
+	errors: {
+		noSuchMessage: {
+			message: 'No such message.',
+			code: 'NO_SUCH_MESSAGE',
+			id: '36b67f0e-66a6-414b-83df-992a55294f17',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		messageId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['messageId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const message = await this.chatService.findMyMessageById(me.id, ps.messageId);
+			if (message == null) {
+				throw new ApiError(meta.errors.noSuchMessage);
+			}
+			await this.chatService.deleteMessage(message);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/react.ts b/packages/backend/src/server/api/endpoints/chat/messages/react.ts
new file mode 100644
index 0000000000..561e36ed19
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/messages/react.ts
@@ -0,0 +1,49 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'write:chat',
+
+	res: {
+	},
+
+	errors: {
+		noSuchMessage: {
+			message: 'No such message.',
+			code: 'NO_SUCH_MESSAGE',
+			id: '9b5839b9-0ba0-4351-8c35-37082093d200',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		messageId: { type: 'string', format: 'misskey:id' },
+		reaction: { type: 'string' },
+	},
+	required: ['messageId', 'reaction'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.react(ps.messageId, me.id, ps.reaction);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/room-timeline.ts b/packages/backend/src/server/api/endpoints/chat/messages/room-timeline.ts
new file mode 100644
index 0000000000..ccc0030403
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/messages/room-timeline.ts
@@ -0,0 +1,73 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'read:chat',
+
+	res: {
+		type: 'array',
+		optional: false, nullable: false,
+		items: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'ChatMessageLite',
+		},
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: 'c4d9f88c-9270-4632-b032-6ed8cee36f7f',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
+		sinceId: { type: 'string', format: 'misskey:id' },
+		untilId: { type: 'string', format: 'misskey:id' },
+		roomId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['roomId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatEntityService: ChatEntityService,
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const room = await this.chatService.findRoomById(ps.roomId);
+			if (room == null) {
+				throw new ApiError(meta.errors.noSuchRoom);
+			}
+
+			if (!(await this.chatService.isRoomMember(room, me.id))) {
+				throw new ApiError(meta.errors.noSuchRoom);
+			}
+
+			const messages = await this.chatService.roomTimeline(room.id, ps.limit, ps.sinceId, ps.untilId);
+
+			this.chatService.readRoomChatMessage(me.id, room.id);
+
+			return await this.chatEntityService.packMessagesLiteForRoom(messages);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/search.ts b/packages/backend/src/server/api/endpoints/chat/messages/search.ts
new file mode 100644
index 0000000000..4c989e5ca9
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/messages/search.ts
@@ -0,0 +1,76 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'read:chat',
+
+	res: {
+		type: 'array',
+		optional: false, nullable: false,
+		items: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'ChatMessage',
+		},
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: '460b3669-81b0-4dc9-a997-44442141bf83',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		query: { type: 'string', minLength: 1, maxLength: 256 },
+		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
+		userId: { type: 'string', format: 'misskey:id', nullable: true },
+		roomId: { type: 'string', format: 'misskey:id', nullable: true },
+	},
+	required: ['query'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatEntityService: ChatEntityService,
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			if (ps.roomId != null) {
+				const room = await this.chatService.findRoomById(ps.roomId);
+				if (room == null) {
+					throw new ApiError(meta.errors.noSuchRoom);
+				}
+
+				if (!(await this.chatService.isRoomMember(room, me.id))) {
+					throw new ApiError(meta.errors.noSuchRoom);
+				}
+			}
+
+			const messages = await this.chatService.searchMessages(me.id, ps.query, ps.limit, {
+				userId: ps.userId,
+				roomId: ps.roomId,
+			});
+
+			return await this.chatEntityService.packMessagesDetailed(messages, me);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/show.ts b/packages/backend/src/server/api/endpoints/chat/messages/show.ts
new file mode 100644
index 0000000000..371f7a7071
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/messages/show.ts
@@ -0,0 +1,63 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { GetterService } from '@/server/api/GetterService.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+import { ApiError } from '@/server/api/error.js';
+import { RoleService } from '@/core/RoleService.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'read:chat',
+
+	res: {
+		type: 'object',
+		optional: false, nullable: false,
+		ref: 'ChatMessage',
+	},
+
+	errors: {
+		noSuchMessage: {
+			message: 'No such message.',
+			code: 'NO_SUCH_MESSAGE',
+			id: '3710865b-1848-4da9-8d61-cfed15510b93',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		messageId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['messageId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+		private roleService: RoleService,
+		private chatEntityService: ChatEntityService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const message = await this.chatService.findMessageById(ps.messageId);
+			if (message == null) {
+				throw new ApiError(meta.errors.noSuchMessage);
+			}
+			if (message.fromUserId !== me.id && message.toUserId !== me.id && !(await this.roleService.isModerator(me))) {
+				throw new ApiError(meta.errors.noSuchMessage);
+			}
+			return this.chatEntityService.packMessageDetailed(message, me);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/user-timeline.ts b/packages/backend/src/server/api/endpoints/chat/messages/user-timeline.ts
new file mode 100644
index 0000000000..9d308d79b0
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/messages/user-timeline.ts
@@ -0,0 +1,71 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { GetterService } from '@/server/api/GetterService.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'read:chat',
+
+	res: {
+		type: 'array',
+		optional: false, nullable: false,
+		items: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'ChatMessageLite',
+		},
+	},
+
+	errors: {
+		noSuchUser: {
+			message: 'No such user.',
+			code: 'NO_SUCH_USER',
+			id: '11795c64-40ea-4198-b06e-3c873ed9039d',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
+		sinceId: { type: 'string', format: 'misskey:id' },
+		untilId: { type: 'string', format: 'misskey:id' },
+		userId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['userId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatEntityService: ChatEntityService,
+		private chatService: ChatService,
+		private getterService: GetterService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const other = await this.getterService.getUser(ps.userId).catch(err => {
+				if (err.id === '15348ddd-432d-49c2-8a5a-8069753becff') throw new ApiError(meta.errors.noSuchUser);
+				throw err;
+			});
+
+			const messages = await this.chatService.userTimeline(me.id, other.id, ps.limit, ps.sinceId, ps.untilId);
+
+			this.chatService.readUserChatMessage(me.id, other.id);
+
+			return await this.chatEntityService.packMessagesLiteFor1on1(messages);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/create.ts b/packages/backend/src/server/api/endpoints/chat/rooms/create.ts
new file mode 100644
index 0000000000..fa4cc8ceb4
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/create.ts
@@ -0,0 +1,62 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import ms from 'ms';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ApiError } from '@/server/api/error.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+	requiredRolePolicy: 'canChat',
+
+	prohibitMoved: true,
+
+	kind: 'write:chat',
+
+	limit: {
+		duration: ms('1day'),
+		max: 10,
+	},
+
+	res: {
+		type: 'object',
+		optional: false, nullable: false,
+		ref: 'ChatRoom',
+	},
+
+	errors: {
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		name: { type: 'string', maxLength: 256 },
+		description: { type: 'string', maxLength: 1024 },
+	},
+	required: ['name'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+		private chatEntityService: ChatEntityService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const room = await this.chatService.createRoom(me, {
+				name: ps.name,
+				description: ps.description ?? '',
+			});
+			return await this.chatEntityService.packRoom(room);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/delete.ts b/packages/backend/src/server/api/endpoints/chat/rooms/delete.ts
new file mode 100644
index 0000000000..2ef0a778f1
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/delete.ts
@@ -0,0 +1,52 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'write:chat',
+
+	res: {
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: 'd4e3753d-97bf-4a19-ab8e-21080fbc0f4b',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		roomId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['roomId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const room = await this.chatService.findMyRoomById(me.id, ps.roomId);
+			if (room == null) {
+				throw new ApiError(meta.errors.noSuchRoom);
+			}
+			await this.chatService.deleteRoom(room);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/invitations/create.ts b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/create.ts
new file mode 100644
index 0000000000..5da4a1a772
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/create.ts
@@ -0,0 +1,68 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import ms from 'ms';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ApiError } from '@/server/api/error.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+	requiredRolePolicy: 'canChat',
+
+	prohibitMoved: true,
+
+	kind: 'write:chat',
+
+	limit: {
+		duration: ms('1day'),
+		max: 50,
+	},
+
+	res: {
+		type: 'object',
+		optional: false, nullable: false,
+		ref: 'ChatRoomInvitation',
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: '916f9507-49ba-4e90-b57f-1fd4deaa47a5',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		roomId: { type: 'string', format: 'misskey:id' },
+		userId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['roomId', 'userId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+		private chatEntityService: ChatEntityService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const room = await this.chatService.findMyRoomById(me.id, ps.roomId);
+			if (room == null) {
+				throw new ApiError(meta.errors.noSuchRoom);
+			}
+			const invitation = await this.chatService.createRoomInvitation(me.id, room.id, ps.userId);
+			return await this.chatEntityService.packRoomInvitation(invitation, me);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/invitations/ignore.ts b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/ignore.ts
new file mode 100644
index 0000000000..8c017f7d01
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/ignore.ts
@@ -0,0 +1,48 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'write:chat',
+
+	res: {
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: '5130557e-5a11-4cfb-9cc5-fe60cda5de0d',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		roomId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['roomId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.ignoreRoomInvitation(me.id, ps.roomId);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/invitations/inbox.ts b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/inbox.ts
new file mode 100644
index 0000000000..07337480fc
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/inbox.ts
@@ -0,0 +1,54 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'read:chat',
+
+	res: {
+		type: 'array',
+		optional: false, nullable: false,
+		items: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'ChatRoomInvitation',
+		},
+	},
+
+	errors: {
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		limit: { type: 'integer', minimum: 1, maximum: 100, default: 30 },
+		sinceId: { type: 'string', format: 'misskey:id' },
+		untilId: { type: 'string', format: 'misskey:id' },
+	},
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatEntityService: ChatEntityService,
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const invitations = await this.chatService.getReceivedRoomInvitationsWithPagination(me.id, ps.limit, ps.sinceId, ps.untilId);
+			return this.chatEntityService.packRoomInvitations(invitations, me);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/join.ts b/packages/backend/src/server/api/endpoints/chat/rooms/join.ts
new file mode 100644
index 0000000000..dbd4d1ea5a
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/join.ts
@@ -0,0 +1,48 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'write:chat',
+
+	res: {
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: '84416476-5ce8-4a2c-b568-9569f1b10733',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		roomId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['roomId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.joinToRoom(me.id, ps.roomId);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/joining.ts b/packages/backend/src/server/api/endpoints/chat/rooms/joining.ts
new file mode 100644
index 0000000000..c4c6253236
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/joining.ts
@@ -0,0 +1,58 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'read:chat',
+
+	res: {
+		type: 'array',
+		optional: false, nullable: false,
+		items: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'ChatRoomMembership',
+		},
+	},
+
+	errors: {
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		limit: { type: 'integer', minimum: 1, maximum: 100, default: 30 },
+		sinceId: { type: 'string', format: 'misskey:id' },
+		untilId: { type: 'string', format: 'misskey:id' },
+	},
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+		private chatEntityService: ChatEntityService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const memberships = await this.chatService.getMyMemberships(me.id, ps.limit, ps.sinceId, ps.untilId);
+
+			return this.chatEntityService.packRoomMemberships(memberships, me, {
+				populateUser: false,
+				populateRoom: true,
+			});
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/leave.ts b/packages/backend/src/server/api/endpoints/chat/rooms/leave.ts
new file mode 100644
index 0000000000..724ad61f7e
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/leave.ts
@@ -0,0 +1,48 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'write:chat',
+
+	res: {
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: 'cb7f3179-50e8-4389-8c30-dbe2650a67c9',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		roomId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['roomId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.leaveRoom(me.id, ps.roomId);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/members.ts b/packages/backend/src/server/api/endpoints/chat/rooms/members.ts
new file mode 100644
index 0000000000..407bfe74f1
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/members.ts
@@ -0,0 +1,74 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ApiError } from '@/server/api/error.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'write:chat',
+
+	res: {
+		type: 'array',
+		optional: false, nullable: false,
+		items: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'ChatRoomMembership',
+		},
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: '7b9fe84c-eafc-4d21-bf89-485458ed2c18',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		roomId: { type: 'string', format: 'misskey:id' },
+		limit: { type: 'integer', minimum: 1, maximum: 100, default: 30 },
+		sinceId: { type: 'string', format: 'misskey:id' },
+		untilId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['roomId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+		private chatEntityService: ChatEntityService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const room = await this.chatService.findRoomById(ps.roomId);
+			if (room == null) {
+				throw new ApiError(meta.errors.noSuchRoom);
+			}
+
+			if (!(await this.chatService.isRoomMember(room, me.id))) {
+				throw new ApiError(meta.errors.noSuchRoom);
+			}
+
+			const memberships = await this.chatService.getRoomMembershipsWithPagination(room.id, ps.limit, ps.sinceId, ps.untilId);
+
+			return this.chatEntityService.packRoomMemberships(memberships, me, {
+				populateUser: true,
+				populateRoom: false,
+			});
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/mute.ts b/packages/backend/src/server/api/endpoints/chat/rooms/mute.ts
new file mode 100644
index 0000000000..5208b8a253
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/mute.ts
@@ -0,0 +1,49 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'write:chat',
+
+	res: {
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: 'c2cde4eb-8d0f-42f1-8f2f-c4d6bfc8e5df',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		roomId: { type: 'string', format: 'misskey:id' },
+		mute: { type: 'boolean' },
+	},
+	required: ['roomId', 'mute'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.muteRoom(me.id, ps.roomId, ps.mute);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/owned.ts b/packages/backend/src/server/api/endpoints/chat/rooms/owned.ts
new file mode 100644
index 0000000000..6516120bca
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/owned.ts
@@ -0,0 +1,54 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+import { ApiError } from '@/server/api/error.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'read:chat',
+
+	res: {
+		type: 'array',
+		optional: false, nullable: false,
+		items: {
+			type: 'object',
+			optional: false, nullable: false,
+			ref: 'ChatRoom',
+		},
+	},
+
+	errors: {
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		limit: { type: 'integer', minimum: 1, maximum: 100, default: 30 },
+		sinceId: { type: 'string', format: 'misskey:id' },
+		untilId: { type: 'string', format: 'misskey:id' },
+	},
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatEntityService: ChatEntityService,
+		private chatService: ChatService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const rooms = await this.chatService.getOwnedRoomsWithPagination(me.id, ps.limit, ps.sinceId, ps.untilId);
+			return this.chatEntityService.packRooms(rooms, me);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/show.ts b/packages/backend/src/server/api/endpoints/chat/rooms/show.ts
new file mode 100644
index 0000000000..547618ee7d
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/show.ts
@@ -0,0 +1,58 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ApiError } from '@/server/api/error.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'read:chat',
+
+	res: {
+		type: 'object',
+		optional: false, nullable: false,
+		ref: 'ChatRoom',
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: '857ae02f-8759-4d20-9adb-6e95fffe4fd7',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		roomId: { type: 'string', format: 'misskey:id' },
+	},
+	required: ['roomId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+		private chatEntityService: ChatEntityService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const room = await this.chatService.findRoomById(ps.roomId);
+			if (room == null) {
+				throw new ApiError(meta.errors.noSuchRoom);
+			}
+
+			return this.chatEntityService.packRoom(room, me);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/update.ts b/packages/backend/src/server/api/endpoints/chat/rooms/update.ts
new file mode 100644
index 0000000000..6f2a9c10b5
--- /dev/null
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/update.ts
@@ -0,0 +1,65 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Inject, Injectable } from '@nestjs/common';
+import { Endpoint } from '@/server/api/endpoint-base.js';
+import { DI } from '@/di-symbols.js';
+import { ChatService } from '@/core/ChatService.js';
+import { ApiError } from '@/server/api/error.js';
+import { ChatEntityService } from '@/core/entities/ChatEntityService.js';
+
+export const meta = {
+	tags: ['chat'],
+
+	requireCredential: true,
+
+	kind: 'write:chat',
+
+	res: {
+		type: 'object',
+		optional: false, nullable: false,
+		ref: 'ChatRoom',
+	},
+
+	errors: {
+		noSuchRoom: {
+			message: 'No such room.',
+			code: 'NO_SUCH_ROOM',
+			id: 'fcdb0f92-bda6-47f9-bd05-343e0e020932',
+		},
+	},
+} as const;
+
+export const paramDef = {
+	type: 'object',
+	properties: {
+		roomId: { type: 'string', format: 'misskey:id' },
+		name: { type: 'string', maxLength: 256 },
+		description: { type: 'string', maxLength: 1024 },
+	},
+	required: ['roomId'],
+} as const;
+
+@Injectable()
+export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
+	constructor(
+		private chatService: ChatService,
+		private chatEntityService: ChatEntityService,
+	) {
+		super(meta, paramDef, async (ps, me) => {
+			const room = await this.chatService.findMyRoomById(me.id, ps.roomId);
+			if (room == null) {
+				throw new ApiError(meta.errors.noSuchRoom);
+			}
+
+			const updated = await this.chatService.updateRoom(room, {
+				name: ps.name,
+				description: ps.description,
+			});
+
+			return this.chatEntityService.packRoom(updated, me);
+		});
+	}
+}
diff --git a/packages/backend/src/server/api/endpoints/i/notifications-grouped.ts b/packages/backend/src/server/api/endpoints/i/notifications-grouped.ts
index dc6ffd3e02..88d7f51c26 100644
--- a/packages/backend/src/server/api/endpoints/i/notifications-grouped.ts
+++ b/packages/backend/src/server/api/endpoints/i/notifications-grouped.ts
@@ -9,7 +9,6 @@ import { Inject, Injectable } from '@nestjs/common';
 import type { NotesRepository } from '@/models/_.js';
 import { obsoleteNotificationTypes, groupedNotificationTypes, FilterUnionByProperty } from '@/types.js';
 import { Endpoint } from '@/server/api/endpoint-base.js';
-import { NoteReadService } from '@/core/NoteReadService.js';
 import { NotificationEntityService } from '@/core/entities/NotificationEntityService.js';
 import { NotificationService } from '@/core/NotificationService.js';
 import { DI } from '@/di-symbols.js';
@@ -63,13 +62,9 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		@Inject(DI.redis)
 		private redisClient: Redis.Redis,
 
-		@Inject(DI.notesRepository)
-		private notesRepository: NotesRepository,
-
 		private idService: IdService,
 		private notificationEntityService: NotificationEntityService,
 		private notificationService: NotificationService,
-		private noteReadService: NoteReadService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
 			const EXTRA_LIMIT = 100;
@@ -162,14 +157,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 			}
 
 			groupedNotifications = groupedNotifications.slice(0, ps.limit);
-			const noteIds = groupedNotifications
-				.filter((notification): notification is FilterUnionByProperty<MiNotification, 'type', 'mention' | 'reply' | 'quote'> => ['mention', 'reply', 'quote'].includes(notification.type))
-				.map(notification => notification.noteId!);
-
-			if (noteIds.length > 0) {
-				const notes = await this.notesRepository.findBy({ id: In(noteIds) });
-				this.noteReadService.read(me.id, notes);
-			}
 
 			return await this.notificationEntityService.packGroupedMany(groupedNotifications, me.id);
 		});
diff --git a/packages/backend/src/server/api/endpoints/i/notifications.ts b/packages/backend/src/server/api/endpoints/i/notifications.ts
index 2f619380e9..be8d0cfb34 100644
--- a/packages/backend/src/server/api/endpoints/i/notifications.ts
+++ b/packages/backend/src/server/api/endpoints/i/notifications.ts
@@ -9,7 +9,6 @@ import { Inject, Injectable } from '@nestjs/common';
 import type { NotesRepository } from '@/models/_.js';
 import { FilterUnionByProperty, notificationTypes, obsoleteNotificationTypes } from '@/types.js';
 import { Endpoint } from '@/server/api/endpoint-base.js';
-import { NoteReadService } from '@/core/NoteReadService.js';
 import { NotificationEntityService } from '@/core/entities/NotificationEntityService.js';
 import { NotificationService } from '@/core/NotificationService.js';
 import { DI } from '@/di-symbols.js';
@@ -69,7 +68,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private idService: IdService,
 		private notificationEntityService: NotificationEntityService,
 		private notificationService: NotificationService,
-		private noteReadService: NoteReadService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
 			// includeTypes が空の場合はクエリしない
@@ -136,15 +134,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				this.notificationService.readAllNotification(me.id);
 			}
 
-			const noteIds = notifications
-				.filter((notification): notification is FilterUnionByProperty<MiNotification, 'type', 'mention' | 'reply' | 'quote'> => ['mention', 'reply', 'quote'].includes(notification.type))
-				.map(notification => notification.noteId);
-
-			if (noteIds.length > 0) {
-				const notes = await this.notesRepository.findBy({ id: In(noteIds) });
-				this.noteReadService.read(me.id, notes);
-			}
-
 			return await this.notificationEntityService.packMany(notifications, me.id);
 		});
 	}
diff --git a/packages/backend/src/server/api/endpoints/i/read-all-unread-notes.ts b/packages/backend/src/server/api/endpoints/i/read-all-unread-notes.ts
deleted file mode 100644
index d1a8eccb1d..0000000000
--- a/packages/backend/src/server/api/endpoints/i/read-all-unread-notes.ts
+++ /dev/null
@@ -1,45 +0,0 @@
-/*
- * SPDX-FileCopyrightText: syuilo and misskey-project
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-
-import { Inject, Injectable } from '@nestjs/common';
-import { Endpoint } from '@/server/api/endpoint-base.js';
-import type { NoteUnreadsRepository } from '@/models/_.js';
-import { GlobalEventService } from '@/core/GlobalEventService.js';
-import { DI } from '@/di-symbols.js';
-
-export const meta = {
-	tags: ['account'],
-
-	requireCredential: true,
-
-	kind: 'write:account',
-} as const;
-
-export const paramDef = {
-	type: 'object',
-	properties: {},
-	required: [],
-} as const;
-
-@Injectable()
-export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
-	constructor(
-		@Inject(DI.noteUnreadsRepository)
-		private noteUnreadsRepository: NoteUnreadsRepository,
-
-		private globalEventService: GlobalEventService,
-	) {
-		super(meta, paramDef, async (ps, me) => {
-			// Remove documents
-			await this.noteUnreadsRepository.delete({
-				userId: me.id,
-			});
-
-			// 全て既読になったイベントを発行
-			this.globalEventService.publishMainStream(me.id, 'readAllUnreadMentions');
-			this.globalEventService.publishMainStream(me.id, 'readAllUnreadSpecifiedNotes');
-		});
-	}
-}
diff --git a/packages/backend/src/server/api/endpoints/i/update.ts b/packages/backend/src/server/api/endpoints/i/update.ts
index 4c72879b73..baf397bf06 100644
--- a/packages/backend/src/server/api/endpoints/i/update.ts
+++ b/packages/backend/src/server/api/endpoints/i/update.ts
@@ -190,6 +190,7 @@ export const paramDef = {
 		autoSensitive: { type: 'boolean' },
 		followingVisibility: { type: 'string', enum: ['public', 'followers', 'private'] },
 		followersVisibility: { type: 'string', enum: ['public', 'followers', 'private'] },
+		chatScope: { type: 'string', enum: ['everyone', 'followers', 'following', 'mutual', 'none'] },
 		pinnedPageId: { type: 'string', format: 'misskey:id', nullable: true },
 		mutedWords: muteWords,
 		hardMutedWords: muteWords,
@@ -288,6 +289,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 			if (ps.birthday !== undefined) profileUpdates.birthday = ps.birthday;
 			if (ps.followingVisibility !== undefined) profileUpdates.followingVisibility = ps.followingVisibility;
 			if (ps.followersVisibility !== undefined) profileUpdates.followersVisibility = ps.followersVisibility;
+			if (ps.chatScope !== undefined) updates.chatScope = ps.chatScope;
 
 			function checkMuteWordCount(mutedWords: (string[] | string)[], limit: number) {
 				// TODO: ちゃんと数える
diff --git a/packages/backend/src/server/api/endpoints/notes/mentions.ts b/packages/backend/src/server/api/endpoints/notes/mentions.ts
index 5558dd3a8b..18a3915ab5 100644
--- a/packages/backend/src/server/api/endpoints/notes/mentions.ts
+++ b/packages/backend/src/server/api/endpoints/notes/mentions.ts
@@ -9,7 +9,6 @@ import type { NotesRepository, FollowingsRepository } from '@/models/_.js';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import { QueryService } from '@/core/QueryService.js';
 import { NoteEntityService } from '@/core/entities/NoteEntityService.js';
-import { NoteReadService } from '@/core/NoteReadService.js';
 import { DI } from '@/di-symbols.js';
 
 export const meta = {
@@ -52,7 +51,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 
 		private noteEntityService: NoteEntityService,
 		private queryService: QueryService,
-		private noteReadService: NoteReadService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
 			const followingQuery = this.followingsRepository.createQueryBuilder('following')
@@ -89,8 +87,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 
 			const mentions = await query.limit(ps.limit).getMany();
 
-			this.noteReadService.read(me.id, mentions);
-
 			return await this.noteEntityService.packMany(mentions, me);
 		});
 	}
diff --git a/packages/backend/src/server/api/endpoints/notes/thread-muting/create.ts b/packages/backend/src/server/api/endpoints/notes/thread-muting/create.ts
index 732d644a29..29c6aa7434 100644
--- a/packages/backend/src/server/api/endpoints/notes/thread-muting/create.ts
+++ b/packages/backend/src/server/api/endpoints/notes/thread-muting/create.ts
@@ -9,7 +9,6 @@ import type { NotesRepository, NoteThreadMutingsRepository } from '@/models/_.js
 import { IdService } from '@/core/IdService.js';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import { GetterService } from '@/server/api/GetterService.js';
-import { NoteReadService } from '@/core/NoteReadService.js';
 import { DI } from '@/di-symbols.js';
 import { ApiError } from '../../../error.js';
 
@@ -52,7 +51,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private noteThreadMutingsRepository: NoteThreadMutingsRepository,
 
 		private getterService: GetterService,
-		private noteReadService: NoteReadService,
 		private idService: IdService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
@@ -69,8 +67,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				}],
 			});
 
-			await this.noteReadService.read(me.id, mutedNotes);
-
 			await this.noteThreadMutingsRepository.insert({
 				id: this.idService.gen(),
 				threadId: note.threadId ?? note.id,
diff --git a/packages/backend/src/server/api/stream/ChannelsService.ts b/packages/backend/src/server/api/stream/ChannelsService.ts
index 253409259f..c0ef589dea 100644
--- a/packages/backend/src/server/api/stream/ChannelsService.ts
+++ b/packages/backend/src/server/api/stream/ChannelsService.ts
@@ -19,6 +19,8 @@ import { AntennaChannelService } from './channels/antenna.js';
 import { DriveChannelService } from './channels/drive.js';
 import { HashtagChannelService } from './channels/hashtag.js';
 import { RoleTimelineChannelService } from './channels/role-timeline.js';
+import { ChatUserChannelService } from './channels/chat-user.js';
+import { ChatRoomChannelService } from './channels/chat-room.js';
 import { ReversiChannelService } from './channels/reversi.js';
 import { ReversiGameChannelService } from './channels/reversi-game.js';
 import { type MiChannelService } from './channel.js';
@@ -40,6 +42,8 @@ export class ChannelsService {
 		private serverStatsChannelService: ServerStatsChannelService,
 		private queueStatsChannelService: QueueStatsChannelService,
 		private adminChannelService: AdminChannelService,
+		private chatUserChannelService: ChatUserChannelService,
+		private chatRoomChannelService: ChatRoomChannelService,
 		private reversiChannelService: ReversiChannelService,
 		private reversiGameChannelService: ReversiGameChannelService,
 	) {
@@ -62,6 +66,8 @@ export class ChannelsService {
 			case 'serverStats': return this.serverStatsChannelService;
 			case 'queueStats': return this.queueStatsChannelService;
 			case 'admin': return this.adminChannelService;
+			case 'chatUser': return this.chatUserChannelService;
+			case 'chatRoom': return this.chatRoomChannelService;
 			case 'reversi': return this.reversiChannelService;
 			case 'reversiGame': return this.reversiGameChannelService;
 
diff --git a/packages/backend/src/server/api/stream/Connection.ts b/packages/backend/src/server/api/stream/Connection.ts
index 0fb5238c78..c9801d8314 100644
--- a/packages/backend/src/server/api/stream/Connection.ts
+++ b/packages/backend/src/server/api/stream/Connection.ts
@@ -7,7 +7,6 @@ import * as WebSocket from 'ws';
 import type { MiUser } from '@/models/User.js';
 import type { MiAccessToken } from '@/models/AccessToken.js';
 import type { Packed } from '@/misc/json-schema.js';
-import type { NoteReadService } from '@/core/NoteReadService.js';
 import type { NotificationService } from '@/core/NotificationService.js';
 import { bindThis } from '@/decorators.js';
 import { CacheService } from '@/core/CacheService.js';
@@ -45,7 +44,6 @@ export default class Connection {
 
 	constructor(
 		private channelsService: ChannelsService,
-		private noteReadService: NoteReadService,
 		private notificationService: NotificationService,
 		private cacheService: CacheService,
 		private channelFollowingService: ChannelFollowingService,
@@ -119,7 +117,7 @@ export default class Connection {
 			case 'readNotification': this.onReadNotification(body); break;
 			case 'subNote': this.onSubscribeNote(body); break;
 			case 's': this.onSubscribeNote(body); break; // alias
-			case 'sr': this.onSubscribeNote(body); this.readNote(body); break;
+			case 'sr': this.onSubscribeNote(body); break;
 			case 'unsubNote': this.onUnsubscribeNote(body); break;
 			case 'un': this.onUnsubscribeNote(body); break; // alias
 			case 'connect': this.onChannelConnectRequested(body); break;
@@ -155,19 +153,6 @@ export default class Connection {
 	}
 
 	@bindThis
-	private readNote(body: JsonValue | undefined) {
-		if (!isJsonObject(body)) return;
-		const id = body.id;
-
-		const note = this.cachedNotes.find(n => n.id === id);
-		if (note == null) return;
-
-		if (this.user && (note.userId !== this.user.id)) {
-			this.noteReadService.read(this.user.id, [note]);
-		}
-	}
-
-	@bindThis
 	private onReadNotification(payload: JsonValue | undefined) {
 		this.notificationService.readAllNotification(this.user!.id);
 	}
diff --git a/packages/backend/src/server/api/stream/channels/chat-room.ts b/packages/backend/src/server/api/stream/channels/chat-room.ts
new file mode 100644
index 0000000000..e989969345
--- /dev/null
+++ b/packages/backend/src/server/api/stream/channels/chat-room.ts
@@ -0,0 +1,78 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Injectable } from '@nestjs/common';
+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 MiChannelService } from '../channel.js';
+
+class ChatRoomChannel extends Channel {
+	public readonly chName = 'chatRoom';
+	public static shouldShare = false;
+	public static requireCredential = true as const;
+	public static kind = 'read:chat';
+	private roomId: string;
+
+	constructor(
+		private chatService: ChatService,
+
+		id: string,
+		connection: Channel['connection'],
+	) {
+		super(id, connection);
+	}
+
+	@bindThis
+	public async init(params: JsonObject) {
+		if (typeof params.roomId !== 'string') return;
+		this.roomId = params.roomId;
+
+		this.subscriber.on(`chatRoomStream:${this.roomId}`, this.onEvent);
+	}
+
+	@bindThis
+	private async onEvent(data: GlobalEvents['chat']['payload']) {
+		this.send(data.type, data.body);
+	}
+
+	@bindThis
+	public onMessage(type: string, body: any) {
+		switch (type) {
+			case 'read':
+				if (this.roomId) {
+					this.chatService.readRoomChatMessage(this.user!.id, this.roomId);
+				}
+				break;
+		}
+	}
+
+	@bindThis
+	public dispose() {
+		this.subscriber.off(`chatRoomStream:${this.roomId}`, this.onEvent);
+	}
+}
+
+@Injectable()
+export class ChatRoomChannelService implements MiChannelService<true> {
+	public readonly shouldShare = ChatRoomChannel.shouldShare;
+	public readonly requireCredential = ChatRoomChannel.requireCredential;
+	public readonly kind = ChatRoomChannel.kind;
+
+	constructor(
+		private chatService: ChatService,
+	) {
+	}
+
+	@bindThis
+	public create(id: string, connection: Channel['connection']): ChatRoomChannel {
+		return new ChatRoomChannel(
+			this.chatService,
+			id,
+			connection,
+		);
+	}
+}
diff --git a/packages/backend/src/server/api/stream/channels/chat-user.ts b/packages/backend/src/server/api/stream/channels/chat-user.ts
new file mode 100644
index 0000000000..c4e898cd5b
--- /dev/null
+++ b/packages/backend/src/server/api/stream/channels/chat-user.ts
@@ -0,0 +1,78 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { Injectable } from '@nestjs/common';
+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 MiChannelService } from '../channel.js';
+
+class ChatUserChannel extends Channel {
+	public readonly chName = 'chatUser';
+	public static shouldShare = false;
+	public static requireCredential = true as const;
+	public static kind = 'read:chat';
+	private otherId: string;
+
+	constructor(
+		private chatService: ChatService,
+
+		id: string,
+		connection: Channel['connection'],
+	) {
+		super(id, connection);
+	}
+
+	@bindThis
+	public async init(params: JsonObject) {
+		if (typeof params.otherId !== 'string') return;
+		this.otherId = params.otherId;
+
+		this.subscriber.on(`chatUserStream:${this.user!.id}-${this.otherId}`, this.onEvent);
+	}
+
+	@bindThis
+	private async onEvent(data: GlobalEvents['chat']['payload']) {
+		this.send(data.type, data.body);
+	}
+
+	@bindThis
+	public onMessage(type: string, body: any) {
+		switch (type) {
+			case 'read':
+				if (this.otherId) {
+					this.chatService.readUserChatMessage(this.user!.id, this.otherId);
+				}
+				break;
+		}
+	}
+
+	@bindThis
+	public dispose() {
+		this.subscriber.off(`chatUserStream:${this.user!.id}-${this.otherId}`, this.onEvent);
+	}
+}
+
+@Injectable()
+export class ChatUserChannelService implements MiChannelService<true> {
+	public readonly shouldShare = ChatUserChannel.shouldShare;
+	public readonly requireCredential = ChatUserChannel.requireCredential;
+	public readonly kind = ChatUserChannel.kind;
+
+	constructor(
+		private chatService: ChatService,
+	) {
+	}
+
+	@bindThis
+	public create(id: string, connection: Channel['connection']): ChatUserChannel {
+		return new ChatUserChannel(
+			this.chatService,
+			id,
+			connection,
+		);
+	}
+}