enhance: チャットの閲覧を無効化できるように (#15765)

* enhance: チャットの閲覧を無効化できるように

* fix

* fix

* fix

* readonlyの説明を追加

* enhance: チャットが無効な場合はチャット関連の設定も隠すように

* fix

* refactor: ChatServiceからApiに関するドメイン知識を排除

40 files changed, 240 insertions, 131 deletions

diff --git a/packages/backend/src/core/ChatService.ts b/packages/backend/src/core/ChatService.ts
index 3984cefc80..b0e8cfb61c 100644
--- a/packages/backend/src/core/ChatService.ts
+++ b/packages/backend/src/core/ChatService.ts
@@ -95,6 +95,40 @@ export class ChatService {
 	}
 
 	@bindThis
+	public async getChatAvailability(userId: MiUser['id']): Promise<{ read: boolean; write: boolean; }> {
+		const policies = await this.roleService.getUserPolicies(userId);
+
+		switch (policies.chatAvailability) {
+			case 'available':
+				return {
+					read: true,
+					write: true,
+				};
+			case 'readonly':
+				return {
+					read: true,
+					write: false,
+				};
+			case 'unavailable':
+				return {
+					read: false,
+					write: false,
+				};
+			default:
+				throw new Error('invalid chat availability (unreachable)');
+		}
+	}
+
+	/** getChatAvailabilityの糖衣。主にAPI呼び出し時に走らせて、権限的に問題ない場合はそのまま続行する */
+	@bindThis
+	public async checkChatAvailability(userId: MiUser['id'], permission: 'read' | 'write') {
+		const policy = await this.getChatAvailability(userId);
+		if (policy[permission] === false) {
+			throw new Error('ROLE_PERMISSION_DENIED');
+		}
+	}
+
+	@bindThis
 	public async createMessageToUser(fromUser: { id: MiUser['id']; host: MiUser['host']; }, toUser: MiUser, params: {
 		text?: string | null;
 		file?: MiDriveFile | null;
@@ -140,7 +174,7 @@ export class ChatService {
 			}
 		}
 
-		if (!(await this.roleService.getUserPolicies(toUser.id)).canChat) {
+		if (!(await this.getChatAvailability(toUser.id)).write) {
 			throw new Error('recipient is cannot chat (policy)');
 		}
 
diff --git a/packages/backend/src/core/RoleService.ts b/packages/backend/src/core/RoleService.ts
index 0a2659ee32..601959cc96 100644
--- a/packages/backend/src/core/RoleService.ts
+++ b/packages/backend/src/core/RoleService.ts
@@ -63,7 +63,7 @@ export type RolePolicies = {
 	canImportFollowing: boolean;
 	canImportMuting: boolean;
 	canImportUserLists: boolean;
-	canChat: boolean;
+	chatAvailability: 'available' | 'readonly' | 'unavailable';
 };
 
 export const DEFAULT_POLICIES: RolePolicies = {
@@ -98,7 +98,7 @@ export const DEFAULT_POLICIES: RolePolicies = {
 	canImportFollowing: true,
 	canImportMuting: true,
 	canImportUserLists: true,
-	canChat: true,
+	chatAvailability: 'available',
 };
 
 @Injectable()
@@ -370,6 +370,12 @@ export class RoleService implements OnApplicationShutdown, OnModuleInit {
 			return aggregate(policies.map(policy => policy.useDefault ? basePolicies[name] : policy.value));
 		}
 
+		function aggregateChatAvailability(vs: RolePolicies['chatAvailability'][]) {
+			if (vs.some(v => v === 'available')) return 'available';
+			if (vs.some(v => v === 'readonly')) return 'readonly';
+			return 'unavailable';
+		}
+
 		return {
 			gtlAvailable: calc('gtlAvailable', vs => vs.some(v => v === true)),
 			ltlAvailable: calc('ltlAvailable', vs => vs.some(v => v === true)),
@@ -402,7 +408,7 @@ 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)),
+			chatAvailability: calc('chatAvailability', aggregateChatAvailability),
 		};
 	}
 
diff --git a/packages/backend/src/core/entities/UserEntityService.ts b/packages/backend/src/core/entities/UserEntityService.ts
index ad8052711c..e252ff509e 100644
--- a/packages/backend/src/core/entities/UserEntityService.ts
+++ b/packages/backend/src/core/entities/UserEntityService.ts
@@ -557,7 +557,7 @@ export class UserEntityService implements OnModuleInit {
 				followersVisibility: profile!.followersVisibility,
 				followingVisibility: profile!.followingVisibility,
 				chatScope: user.chatScope,
-				canChat: this.roleService.getUserPolicies(user.id).then(r => r.canChat),
+				canChat: this.roleService.getUserPolicies(user.id).then(r => r.chatAvailability === 'available'),
 				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,
diff --git a/packages/backend/src/models/json-schema/role.ts b/packages/backend/src/models/json-schema/role.ts
index 6f63dcef2e..1cfcb830e0 100644
--- a/packages/backend/src/models/json-schema/role.ts
+++ b/packages/backend/src/models/json-schema/role.ts
@@ -292,9 +292,10 @@ export const packedRolePoliciesSchema = {
 			type: 'boolean',
 			optional: false, nullable: false,
 		},
-		canChat: {
-			type: 'boolean',
+		chatAvailability: {
+			type: 'string',
 			optional: false, nullable: false,
+			enum: ['available', 'readonly', 'unavailable'],
 		},
 	},
 } as const;
diff --git a/packages/backend/src/server/api/endpoints/chat/history.ts b/packages/backend/src/server/api/endpoints/chat/history.ts
index 7553a751e0..fdd9055106 100644
--- a/packages/backend/src/server/api/endpoints/chat/history.ts
+++ b/packages/backend/src/server/api/endpoints/chat/history.ts
@@ -46,6 +46,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			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);
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
index a988dc60b9..ad2b82e219 100644
--- 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
@@ -16,7 +16,6 @@ export const meta = {
 	tags: ['chat'],
 
 	requireCredential: true,
-	requiredRolePolicy: 'canChat',
 
 	prohibitMoved: true,
 
@@ -74,6 +73,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			const room = await this.chatService.findRoomById(ps.toRoomId);
 			if (room == null) {
 				throw new ApiError(meta.errors.noSuchRoom);
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
index bbaab8a6c3..fa34a7d558 100644
--- 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
@@ -16,7 +16,6 @@ export const meta = {
 	tags: ['chat'],
 
 	requireCredential: true,
-	requiredRolePolicy: 'canChat',
 
 	prohibitMoved: true,
 
@@ -86,6 +85,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			let file = null;
 			if (ps.fileId != null) {
 				file = await this.driveFilesRepository.findOneBy({
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/delete.ts b/packages/backend/src/server/api/endpoints/chat/messages/delete.ts
index 25fc774d4f..63b75fb6a7 100644
--- a/packages/backend/src/server/api/endpoints/chat/messages/delete.ts
+++ b/packages/backend/src/server/api/endpoints/chat/messages/delete.ts
@@ -13,7 +13,6 @@ export const meta = {
 	tags: ['chat'],
 
 	requireCredential: true,
-	requiredRolePolicy: 'canChat',
 
 	kind: 'write:chat',
 
@@ -43,6 +42,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			const message = await this.chatService.findMyMessageById(me.id, ps.messageId);
 			if (message == null) {
 				throw new ApiError(meta.errors.noSuchMessage);
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/react.ts b/packages/backend/src/server/api/endpoints/chat/messages/react.ts
index 0145e380be..5f61e7e992 100644
--- a/packages/backend/src/server/api/endpoints/chat/messages/react.ts
+++ b/packages/backend/src/server/api/endpoints/chat/messages/react.ts
@@ -13,7 +13,6 @@ export const meta = {
 	tags: ['chat'],
 
 	requireCredential: true,
-	requiredRolePolicy: 'canChat',
 
 	kind: 'write:chat',
 
@@ -44,6 +43,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			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
index b6d3356196..c0e344b889 100644
--- a/packages/backend/src/server/api/endpoints/chat/messages/room-timeline.ts
+++ b/packages/backend/src/server/api/endpoints/chat/messages/room-timeline.ts
@@ -54,6 +54,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			const room = await this.chatService.findRoomById(ps.roomId);
 			if (room == null) {
 				throw new ApiError(meta.errors.noSuchRoom);
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/search.ts b/packages/backend/src/server/api/endpoints/chat/messages/search.ts
index 4c989e5ca9..682597f76d 100644
--- a/packages/backend/src/server/api/endpoints/chat/messages/search.ts
+++ b/packages/backend/src/server/api/endpoints/chat/messages/search.ts
@@ -54,6 +54,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			if (ps.roomId != null) {
 				const room = await this.chatService.findRoomById(ps.roomId);
 				if (room == null) {
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/show.ts b/packages/backend/src/server/api/endpoints/chat/messages/show.ts
index 371f7a7071..9a2bbb8742 100644
--- a/packages/backend/src/server/api/endpoints/chat/messages/show.ts
+++ b/packages/backend/src/server/api/endpoints/chat/messages/show.ts
@@ -50,6 +50,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatEntityService: ChatEntityService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			const message = await this.chatService.findMessageById(ps.messageId);
 			if (message == null) {
 				throw new ApiError(meta.errors.noSuchMessage);
diff --git a/packages/backend/src/server/api/endpoints/chat/messages/unreact.ts b/packages/backend/src/server/api/endpoints/chat/messages/unreact.ts
index b97bad8a9c..6784bb6ecf 100644
--- a/packages/backend/src/server/api/endpoints/chat/messages/unreact.ts
+++ b/packages/backend/src/server/api/endpoints/chat/messages/unreact.ts
@@ -13,7 +13,6 @@ export const meta = {
 	tags: ['chat'],
 
 	requireCredential: true,
-	requiredRolePolicy: 'canChat',
 
 	kind: 'write:chat',
 
@@ -44,6 +43,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			await this.chatService.unreact(ps.messageId, me.id, ps.reaction);
 		});
 	}
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
index a35f121bb1..a057e2e088 100644
--- a/packages/backend/src/server/api/endpoints/chat/messages/user-timeline.ts
+++ b/packages/backend/src/server/api/endpoints/chat/messages/user-timeline.ts
@@ -56,6 +56,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private getterService: GetterService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			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;
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/create.ts b/packages/backend/src/server/api/endpoints/chat/rooms/create.ts
index fa4cc8ceb4..68a53f0886 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/create.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/create.ts
@@ -15,7 +15,6 @@ export const meta = {
 	tags: ['chat'],
 
 	requireCredential: true,
-	requiredRolePolicy: 'canChat',
 
 	prohibitMoved: true,
 
@@ -52,6 +51,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatEntityService: ChatEntityService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			const room = await this.chatService.createRoom(me, {
 				name: ps.name,
 				description: ps.description ?? '',
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/delete.ts b/packages/backend/src/server/api/endpoints/chat/rooms/delete.ts
index 1d77a06dd8..82a8e1f30d 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/delete.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/delete.ts
@@ -42,6 +42,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			const room = await this.chatService.findRoomById(ps.roomId);
 			if (room == null) {
 				throw new ApiError(meta.errors.noSuchRoom);
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
index 5da4a1a772..b1f049f2b9 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/invitations/create.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/create.ts
@@ -15,7 +15,6 @@ export const meta = {
 	tags: ['chat'],
 
 	requireCredential: true,
-	requiredRolePolicy: 'canChat',
 
 	prohibitMoved: true,
 
@@ -57,6 +56,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatEntityService: ChatEntityService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			const room = await this.chatService.findMyRoomById(me.id, ps.roomId);
 			if (room == null) {
 				throw new ApiError(meta.errors.noSuchRoom);
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
index 8c017f7d01..b8a228089b 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/invitations/ignore.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/ignore.ts
@@ -42,6 +42,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			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
index 07337480fc..8a02d1c704 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/invitations/inbox.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/inbox.ts
@@ -47,6 +47,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			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/invitations/outbox.ts b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/outbox.ts
index 12d496e94b..0702ba086c 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/invitations/outbox.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/invitations/outbox.ts
@@ -55,6 +55,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatEntityService: ChatEntityService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			const room = await this.chatService.findMyRoomById(me.id, ps.roomId);
 			if (room == null) {
 				throw new ApiError(meta.errors.noSuchRoom);
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/join.ts b/packages/backend/src/server/api/endpoints/chat/rooms/join.ts
index dbd4d1ea5a..d561f9e03f 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/join.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/join.ts
@@ -42,6 +42,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			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
index c4c6253236..ba9242c762 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/joining.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/joining.ts
@@ -47,6 +47,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatEntityService: ChatEntityService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			const memberships = await this.chatService.getMyMemberships(me.id, ps.limit, ps.sinceId, ps.untilId);
 
 			return this.chatEntityService.packRoomMemberships(memberships, me, {
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/leave.ts b/packages/backend/src/server/api/endpoints/chat/rooms/leave.ts
index 724ad61f7e..a3ad0c2d6f 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/leave.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/leave.ts
@@ -42,6 +42,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			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
index 407bfe74f1..f5ffa21d32 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/members.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/members.ts
@@ -54,6 +54,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatEntityService: ChatEntityService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			const room = await this.chatService.findRoomById(ps.roomId);
 			if (room == null) {
 				throw new ApiError(meta.errors.noSuchRoom);
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/mute.ts b/packages/backend/src/server/api/endpoints/chat/rooms/mute.ts
index 5208b8a253..11cbe7b8b9 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/mute.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/mute.ts
@@ -43,6 +43,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			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
index 6516120bca..accf7e1bee 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/owned.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/owned.ts
@@ -47,6 +47,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatService: ChatService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			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
index 547618ee7d..50da210d81 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/show.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/show.ts
@@ -47,6 +47,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatEntityService: ChatEntityService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'read');
+
 			const room = await this.chatService.findRoomById(ps.roomId);
 			if (room == null) {
 				throw new ApiError(meta.errors.noSuchRoom);
diff --git a/packages/backend/src/server/api/endpoints/chat/rooms/update.ts b/packages/backend/src/server/api/endpoints/chat/rooms/update.ts
index 6f2a9c10b5..0cd62cb040 100644
--- a/packages/backend/src/server/api/endpoints/chat/rooms/update.ts
+++ b/packages/backend/src/server/api/endpoints/chat/rooms/update.ts
@@ -49,6 +49,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private chatEntityService: ChatEntityService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			await this.chatService.checkChatAvailability(me.id, 'write');
+
 			const room = await this.chatService.findMyRoomById(me.id, ps.roomId);
 			if (room == null) {
 				throw new ApiError(meta.errors.noSuchRoom);
diff --git a/packages/frontend-shared/js/const.ts b/packages/frontend-shared/js/const.ts
index fa60476b69..de65c3db97 100644
--- a/packages/frontend-shared/js/const.ts
+++ b/packages/frontend-shared/js/const.ts
@@ -108,7 +108,7 @@ export const ROLE_POLICIES = [
 	'canImportFollowing',
 	'canImportMuting',
 	'canImportUserLists',
-	'canChat',
+	'chatAvailability',
 ] as const;
 
 export const DEFAULT_SERVER_ERROR_IMAGE_URL = 'https://xn--931a.moe/assets/error.jpg';
diff --git a/packages/frontend/src/navbar.ts b/packages/frontend/src/navbar.ts
index 185d9e81b7..c0fe0f2b85 100644
--- a/packages/frontend/src/navbar.ts
+++ b/packages/frontend/src/navbar.ts
@@ -114,6 +114,7 @@ export const navbarItemDef = reactive({
 		title: i18n.ts.chat,
 		icon: 'ti ti-messages',
 		to: '/chat',
+		show: computed(() => $i != null && $i.policies.chatAvailability !== 'unavailable'),
 		indicated: computed(() => $i != null && $i.hasUnreadChatMessages),
 	},
 	achievements: {
diff --git a/packages/frontend/src/pages/admin/roles.editor.vue b/packages/frontend/src/pages/admin/roles.editor.vue
index 73119940c1..930a63f5a9 100644
--- a/packages/frontend/src/pages/admin/roles.editor.vue
+++ b/packages/frontend/src/pages/admin/roles.editor.vue
@@ -165,21 +165,24 @@ SPDX-License-Identifier: AGPL-3.0-only
 				</div>
 			</MkFolder>
 
-			<MkFolder v-if="matchQuery([i18n.ts._role._options.canChat, 'canChat'])">
-				<template #label>{{ i18n.ts._role._options.canChat }}</template>
+			<MkFolder v-if="matchQuery([i18n.ts._role._options.chatAvailability, 'chatAvailability'])">
+				<template #label>{{ i18n.ts._role._options.chatAvailability }}</template>
 				<template #suffix>
-					<span v-if="role.policies.canChat.useDefault" :class="$style.useDefaultLabel">{{ i18n.ts._role.useBaseValue }}</span>
-					<span v-else>{{ role.policies.canChat.value ? i18n.ts.yes : i18n.ts.no }}</span>
-					<span :class="$style.priorityIndicator"><i :class="getPriorityIcon(role.policies.canChat)"></i></span>
+					<span v-if="role.policies.chatAvailability.useDefault" :class="$style.useDefaultLabel">{{ i18n.ts._role.useBaseValue }}</span>
+					<span v-else>{{ role.policies.chatAvailability.value === 'available' ? i18n.ts.yes : role.policies.chatAvailability.value === 'readonly' ? i18n.ts.readonly : i18n.ts.no }}</span>
+					<span :class="$style.priorityIndicator"><i :class="getPriorityIcon(role.policies.chatAvailability)"></i></span>
 				</template>
 				<div class="_gaps">
-					<MkSwitch v-model="role.policies.canChat.useDefault" :readonly="readonly">
+					<MkSwitch v-model="role.policies.chatAvailability.useDefault" :readonly="readonly">
 						<template #label>{{ i18n.ts._role.useBaseValue }}</template>
 					</MkSwitch>
-					<MkSwitch v-model="role.policies.canChat.value" :disabled="role.policies.canChat.useDefault" :readonly="readonly">
+					<MkSelect v-model="role.policies.chatAvailability.value" :disabled="role.policies.chatAvailability.useDefault" :readonly="readonly">
 						<template #label>{{ i18n.ts.enable }}</template>
-					</MkSwitch>
-					<MkRange v-model="role.policies.canChat.priority" :min="0" :max="2" :step="1" easing :textConverter="(v) => v === 0 ? i18n.ts._role._priority.low : v === 1 ? i18n.ts._role._priority.middle : v === 2 ? i18n.ts._role._priority.high : ''">
+						<option value="available">{{ i18n.ts.enabled }}</option>
+						<option value="readonly">{{ i18n.ts.readonly }}</option>
+						<option value="unavailable">{{ i18n.ts.disabled }}</option>
+					</MkSelect>
+					<MkRange v-model="role.policies.chatAvailability.priority" :min="0" :max="2" :step="1" easing :textConverter="(v) => v === 0 ? i18n.ts._role._priority.low : v === 1 ? i18n.ts._role._priority.middle : v === 2 ? i18n.ts._role._priority.high : ''">
 						<template #label>{{ i18n.ts._role.priority }}</template>
 					</MkRange>
 				</div>
diff --git a/packages/frontend/src/pages/admin/roles.vue b/packages/frontend/src/pages/admin/roles.vue
index df4efd1271..7c950957cf 100644
--- a/packages/frontend/src/pages/admin/roles.vue
+++ b/packages/frontend/src/pages/admin/roles.vue
@@ -51,12 +51,15 @@ SPDX-License-Identifier: AGPL-3.0-only
 							</MkSwitch>
 						</MkFolder>
 
-						<MkFolder v-if="matchQuery([i18n.ts._role._options.canChat, 'canChat'])">
-							<template #label>{{ i18n.ts._role._options.canChat }}</template>
-							<template #suffix>{{ policies.canChat ? i18n.ts.yes : i18n.ts.no }}</template>
-							<MkSwitch v-model="policies.canChat">
+						<MkFolder v-if="matchQuery([i18n.ts._role._options.chatAvailability, 'chatAvailability'])">
+							<template #label>{{ i18n.ts._role._options.chatAvailability }}</template>
+							<template #suffix>{{ policies.chatAvailability === 'available' ? i18n.ts.yes : policies.chatAvailability === 'readonly' ? i18n.ts.readonly : i18n.ts.no }}</template>
+							<MkSelect v-model="policies.chatAvailability">
 								<template #label>{{ i18n.ts.enable }}</template>
-							</MkSwitch>
+								<option value="available">{{ i18n.ts.enabled }}</option>
+								<option value="readonly">{{ i18n.ts.readonly }}</option>
+								<option value="unavailable">{{ i18n.ts.disabled }}</option>
+							</MkSelect>
 						</MkFolder>
 
 						<MkFolder v-if="matchQuery([i18n.ts._role._options.mentionMax, 'mentionLimit'])">
@@ -295,6 +298,7 @@ import MkInput from '@/components/MkInput.vue';
 import MkFolder from '@/components/MkFolder.vue';
 import MkSwitch from '@/components/MkSwitch.vue';
 import MkButton from '@/components/MkButton.vue';
+import MkSelect from '@/components/MkSelect.vue';
 import MkRange from '@/components/MkRange.vue';
 import MkRolePreview from '@/components/MkRolePreview.vue';
 import * as os from '@/os.js';
diff --git a/packages/frontend/src/pages/chat/XMessage.vue b/packages/frontend/src/pages/chat/XMessage.vue
index eb8b0d79ee..def6ec7d14 100644
--- a/packages/frontend/src/pages/chat/XMessage.vue
+++ b/packages/frontend/src/pages/chat/XMessage.vue
@@ -85,7 +85,7 @@ const isMe = computed(() => props.message.fromUserId === $i.id);
 const urls = computed(() => props.message.text ? extractUrlFromMfm(mfm.parse(props.message.text)) : []);
 
 provide(DI.mfmEmojiReactCallback, (reaction) => {
-	if (!$i.policies.canChat) return;
+	if ($i.policies.chatAvailability !== 'available') return;
 
 	sound.playMisskeySfx('reaction');
 	misskeyApi('chat/messages/react', {
@@ -95,7 +95,7 @@ provide(DI.mfmEmojiReactCallback, (reaction) => {
 });
 
 function react(ev: MouseEvent) {
-	if (!$i.policies.canChat) return;
+	if ($i.policies.chatAvailability !== 'available') return;
 
 	const targetEl = getHTMLElementOrNull(ev.currentTarget ?? ev.target);
 	if (!targetEl) return;
@@ -110,7 +110,7 @@ function react(ev: MouseEvent) {
 }
 
 function onReactionClick(record: Misskey.entities.ChatMessage['reactions'][0]) {
-	if (!$i.policies.canChat) return;
+	if ($i.policies.chatAvailability !== 'available') return;
 
 	if (record.user.id === $i.id) {
 		misskeyApi('chat/messages/unreact', {
@@ -138,7 +138,7 @@ function onContextmenu(ev: MouseEvent) {
 function showMenu(ev: MouseEvent, contextmenu = false) {
 	const menu: MenuItem[] = [];
 
-	if (!isMe.value && $i.policies.canChat) {
+	if (!isMe.value && $i.policies.chatAvailability === 'available') {
 		menu.push({
 			text: i18n.ts.reaction,
 			icon: 'ti ti-mood-plus',
@@ -164,7 +164,7 @@ function showMenu(ev: MouseEvent, contextmenu = false) {
 		type: 'divider',
 	});
 
-	if (isMe.value && $i.policies.canChat) {
+	if (isMe.value && $i.policies.chatAvailability === 'available') {
 		menu.push({
 			text: i18n.ts.delete,
 			icon: 'ti ti-trash',
diff --git a/packages/frontend/src/pages/chat/home.home.vue b/packages/frontend/src/pages/chat/home.home.vue
index 17f0e0fbcd..a8ed891de0 100644
--- a/packages/frontend/src/pages/chat/home.home.vue
+++ b/packages/frontend/src/pages/chat/home.home.vue
@@ -5,9 +5,9 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <template>
 <div class="_gaps">
-	<MkButton v-if="$i.policies.canChat" primary gradate rounded :class="$style.start" @click="start"><i class="ti ti-plus"></i> {{ i18n.ts.startChat }}</MkButton>
+	<MkButton v-if="$i.policies.chatAvailability === 'available'" primary gradate rounded :class="$style.start" @click="start"><i class="ti ti-plus"></i> {{ i18n.ts.startChat }}</MkButton>
 
-	<MkInfo v-else>{{ i18n.ts._chat.chatNotAvailableForThisAccountOrServer }}</MkInfo>
+	<MkInfo v-else>{{ $i.policies.chatAvailability === 'readonly' ? i18n.ts._chat.chatIsReadOnlyForThisAccountOrServer : i18n.ts._chat.chatNotAvailableForThisAccountOrServer }}</MkInfo>
 
 	<MkAd :preferForms="['horizontal', 'horizontal-big']"/>
 
diff --git a/packages/frontend/src/pages/chat/room.vue b/packages/frontend/src/pages/chat/room.vue
index 9942dbeee9..8b351c1ec8 100644
--- a/packages/frontend/src/pages/chat/room.vue
+++ b/packages/frontend/src/pages/chat/room.vue
@@ -6,54 +6,56 @@ SPDX-License-Identifier: AGPL-3.0-only
 <template>
 <PageWithHeader v-model:tab="tab" :reversed="tab === 'chat'" :tabs="headerTabs" :actions="headerActions">
 	<MkSpacer v-if="tab === 'chat'" :contentMax="700">
-		<div v-if="initializing">
-			<MkLoading/>
-		</div>
+		<div class="_gaps">
+			<div v-if="initializing">
+				<MkLoading/>
+			</div>
 
-		<div v-else-if="messages.length === 0">
-			<div class="_gaps" style="text-align: center;">
-				<div>{{ i18n.ts._chat.noMessagesYet }}</div>
-				<template v-if="user">
-					<div v-if="user.chatScope === 'followers'">{{ i18n.ts._chat.thisUserAllowsChatOnlyFromFollowers }}</div>
-					<div v-else-if="user.chatScope === 'following'">{{ i18n.ts._chat.thisUserAllowsChatOnlyFromFollowing }}</div>
-					<div v-else-if="user.chatScope === 'mutual'">{{ i18n.ts._chat.thisUserAllowsChatOnlyFromMutualFollowing }}</div>
-					<div v-else-if="user.chatScope === 'none'">{{ i18n.ts._chat.thisUserNotAllowedChatAnyone }}</div>
-				</template>
-				<template v-else-if="room">
-					<div>{{ i18n.ts._chat.inviteUserToChat }}</div>
-				</template>
+			<div v-else-if="messages.length === 0">
+				<div class="_gaps" style="text-align: center;">
+					<div>{{ i18n.ts._chat.noMessagesYet }}</div>
+					<template v-if="user">
+						<div v-if="user.chatScope === 'followers'">{{ i18n.ts._chat.thisUserAllowsChatOnlyFromFollowers }}</div>
+						<div v-else-if="user.chatScope === 'following'">{{ i18n.ts._chat.thisUserAllowsChatOnlyFromFollowing }}</div>
+						<div v-else-if="user.chatScope === 'mutual'">{{ i18n.ts._chat.thisUserAllowsChatOnlyFromMutualFollowing }}</div>
+						<div v-else-if="user.chatScope === 'none'">{{ i18n.ts._chat.thisUserNotAllowedChatAnyone }}</div>
+					</template>
+					<template v-else-if="room">
+						<div>{{ i18n.ts._chat.inviteUserToChat }}</div>
+					</template>
+				</div>
 			</div>
-		</div>
 
-		<div v-else ref="timelineEl" class="_gaps">
-			<div v-if="canFetchMore">
-				<MkButton :class="$style.more" :wait="moreFetching" primary rounded @click="fetchMore">{{ i18n.ts.loadMore }}</MkButton>
+			<div v-else ref="timelineEl" class="_gaps">
+				<div v-if="canFetchMore">
+					<MkButton :class="$style.more" :wait="moreFetching" primary rounded @click="fetchMore">{{ i18n.ts.loadMore }}</MkButton>
+				</div>
+
+				<TransitionGroup
+					:enterActiveClass="prefer.s.animation ? $style.transition_x_enterActive : ''"
+					:leaveActiveClass="prefer.s.animation ? $style.transition_x_leaveActive : ''"
+					:enterFromClass="prefer.s.animation ? $style.transition_x_enterFrom : ''"
+					:leaveToClass="prefer.s.animation ? $style.transition_x_leaveTo : ''"
+					:moveClass="prefer.s.animation ? $style.transition_x_move : ''"
+					tag="div" class="_gaps"
+				>
+					<template v-for="item in timeline.toReversed()" :key="item.id">
+						<XMessage v-if="item.type === 'item'" :message="item.data"/>
+						<div v-else-if="item.type === 'date'" :class="$style.dateDivider">
+							<span><i class="ti ti-chevron-up"></i> {{ item.nextText }}</span>
+							<span style="height: 1em; width: 1px; background: var(--MI_THEME-divider);"></span>
+							<span>{{ item.prevText }} <i class="ti ti-chevron-down"></i></span>
+						</div>
+					</template>
+				</TransitionGroup>
 			</div>
 
-			<TransitionGroup
-				:enterActiveClass="prefer.s.animation ? $style.transition_x_enterActive : ''"
-				:leaveActiveClass="prefer.s.animation ? $style.transition_x_leaveActive : ''"
-				:enterFromClass="prefer.s.animation ? $style.transition_x_enterFrom : ''"
-				:leaveToClass="prefer.s.animation ? $style.transition_x_leaveTo : ''"
-				:moveClass="prefer.s.animation ? $style.transition_x_move : ''"
-				tag="div" class="_gaps"
-			>
-				<template v-for="item in timeline.toReversed()" :key="item.id">
-					<XMessage v-if="item.type === 'item'" :message="item.data"/>
-					<div v-else-if="item.type === 'date'" :class="$style.dateDivider">
-						<span><i class="ti ti-chevron-up"></i> {{ item.nextText }}</span>
-						<span style="height: 1em; width: 1px; background: var(--MI_THEME-divider);"></span>
-						<span>{{ item.prevText }} <i class="ti ti-chevron-down"></i></span>
-					</div>
-				</template>
-			</TransitionGroup>
-		</div>
+			<div v-if="user && (!user.canChat || user.host !== null)">
+				<MkInfo warn>{{ i18n.ts._chat.chatNotAvailableInOtherAccount }}</MkInfo>
+			</div>
 
-		<div v-if="user && (!user.canChat || user.host !== null)">
-			<MkInfo warn>{{ i18n.ts._chat.chatNotAvailableInOtherAccount }}</MkInfo>
+			<MkInfo v-if="$i.policies.chatAvailability !== 'available'" warn>{{ $i.policies.chatAvailability === 'readonly' ? i18n.ts._chat.chatIsReadOnlyForThisAccountOrServer : i18n.ts._chat.chatNotAvailableForThisAccountOrServer }}</MkInfo>
 		</div>
-
-		<MkInfo v-if="!$i.policies.canChat" warn>{{ i18n.ts._chat.chatNotAvailableForThisAccountOrServer }}</MkInfo>
 	</MkSpacer>
 
 	<MkSpacer v-else-if="tab === 'search'" :contentMax="700">
diff --git a/packages/frontend/src/pages/settings/preferences.vue b/packages/frontend/src/pages/settings/preferences.vue
index 647fed10e3..42a7b486ed 100644
--- a/packages/frontend/src/pages/settings/preferences.vue
+++ b/packages/frontend/src/pages/settings/preferences.vue
@@ -379,44 +379,46 @@ SPDX-License-Identifier: AGPL-3.0-only
 				</MkFolder>
 			</SearchMarker>
 
-			<SearchMarker :keywords="['chat', 'messaging']">
-				<MkFolder>
-					<template #label><SearchLabel>{{ i18n.ts.chat }}</SearchLabel></template>
-					<template #icon><SearchIcon><i class="ti ti-messages"></i></SearchIcon></template>
+			<template v-if="$i.policies.chatAvailability !== 'unavailable'">
+				<SearchMarker :keywords="['chat', 'messaging']">
+					<MkFolder>
+						<template #label><SearchLabel>{{ i18n.ts.chat }}</SearchLabel></template>
+						<template #icon><SearchIcon><i class="ti ti-messages"></i></SearchIcon></template>
 
-					<div class="_gaps_s">
-						<SearchMarker :keywords="['show', 'sender', 'name']">
-							<MkPreferenceContainer k="chat.showSenderName">
-								<MkSwitch v-model="chatShowSenderName">
-									<template #label><SearchLabel>{{ i18n.ts._settings._chat.showSenderName }}</SearchLabel></template>
-								</MkSwitch>
-							</MkPreferenceContainer>
-						</SearchMarker>
+						<div class="_gaps_s">
+							<SearchMarker :keywords="['show', 'sender', 'name']">
+								<MkPreferenceContainer k="chat.showSenderName">
+									<MkSwitch v-model="chatShowSenderName">
+										<template #label><SearchLabel>{{ i18n.ts._settings._chat.showSenderName }}</SearchLabel></template>
+									</MkSwitch>
+								</MkPreferenceContainer>
+							</SearchMarker>
 
-						<SearchMarker :keywords="['send', 'enter', 'newline']">
-							<MkPreferenceContainer k="chat.sendOnEnter">
-								<MkSwitch v-model="chatSendOnEnter">
-									<template #label><SearchLabel>{{ i18n.ts._settings._chat.sendOnEnter }}</SearchLabel></template>
-									<template #caption>
-										<div class="_gaps_s">
-											<div>
-												<b>{{ i18n.ts._settings.ifOn }}:</b>
-												<div>{{ i18n.ts._chat.send }}: Enter</div>
-												<div>{{ i18n.ts._chat.newline }}: Shift + Enter</div>
+							<SearchMarker :keywords="['send', 'enter', 'newline']">
+								<MkPreferenceContainer k="chat.sendOnEnter">
+									<MkSwitch v-model="chatSendOnEnter">
+										<template #label><SearchLabel>{{ i18n.ts._settings._chat.sendOnEnter }}</SearchLabel></template>
+										<template #caption>
+											<div class="_gaps_s">
+												<div>
+													<b>{{ i18n.ts._settings.ifOn }}:</b>
+													<div>{{ i18n.ts._chat.send }}: Enter</div>
+													<div>{{ i18n.ts._chat.newline }}: Shift + Enter</div>
+												</div>
+												<div>
+													<b>{{ i18n.ts._settings.ifOff }}:</b>
+													<div>{{ i18n.ts._chat.send }}: Ctrl + Enter</div>
+													<div>{{ i18n.ts._chat.newline }}: Enter</div>
+												</div>
 											</div>
-											<div>
-												<b>{{ i18n.ts._settings.ifOff }}:</b>
-												<div>{{ i18n.ts._chat.send }}: Ctrl + Enter</div>
-												<div>{{ i18n.ts._chat.newline }}: Enter</div>
-											</div>
-										</div>
-									</template>
-								</MkSwitch>
-							</MkPreferenceContainer>
-						</SearchMarker>
-					</div>
-				</MkFolder>
-			</SearchMarker>
+										</template>
+									</MkSwitch>
+								</MkPreferenceContainer>
+							</SearchMarker>
+						</div>
+					</MkFolder>
+				</SearchMarker>
+			</template>
 
 			<SearchMarker :keywords="['accessibility']">
 				<MkFolder>
@@ -732,6 +734,9 @@ import MkFeatureBanner from '@/components/MkFeatureBanner.vue';
 import { globalEvents } from '@/events.js';
 import { claimAchievement } from '@/utility/achievements.js';
 import { instance } from '@/instance.js';
+import { ensureSignin } from '@/i.js';
+
+const $i = ensureSignin();
 
 const lang = ref(miLocalStorage.getItem('lang'));
 const dataSaver = ref(prefer.s.dataSaver);
diff --git a/packages/frontend/src/pages/settings/privacy.vue b/packages/frontend/src/pages/settings/privacy.vue
index 2f8a697d74..4e6425667e 100644
--- a/packages/frontend/src/pages/settings/privacy.vue
+++ b/packages/frontend/src/pages/settings/privacy.vue
@@ -78,19 +78,26 @@ SPDX-License-Identifier: AGPL-3.0-only
 			</MkSwitch>
 		</SearchMarker>
 
-		<FormSection>
-			<SearchMarker :keywords="['chat']">
-				<MkSelect v-model="chatScope" @update:modelValue="save()">
-					<template #label><SearchLabel>{{ i18n.ts._chat.chatAllowedUsers }}</SearchLabel></template>
-					<option value="everyone">{{ i18n.ts._chat._chatAllowedUsers.everyone }}</option>
-					<option value="followers">{{ i18n.ts._chat._chatAllowedUsers.followers }}</option>
-					<option value="following">{{ i18n.ts._chat._chatAllowedUsers.following }}</option>
-					<option value="mutual">{{ i18n.ts._chat._chatAllowedUsers.mutual }}</option>
-					<option value="none">{{ i18n.ts._chat._chatAllowedUsers.none }}</option>
-					<template #caption>{{ i18n.ts._chat.chatAllowedUsers_note }}</template>
-				</MkSelect>
-			</SearchMarker>
-		</FormSection>
+		<SearchMarker :keywords="['chat']">
+			<FormSection>
+				<template #label><SearchLabel>{{ i18n.ts.chat }}</SearchLabel></template>
+
+				<div class="_gaps_m">
+					<MkInfo v-if="$i.policies.chatAvailability === 'unavailable'">{{ i18n.ts._chat.chatNotAvailableForThisAccountOrServer }}</MkInfo>
+					<SearchMarker :keywords="['chat']">
+						<MkSelect v-model="chatScope" @update:modelValue="save()">
+							<template #label><SearchLabel>{{ i18n.ts._chat.chatAllowedUsers }}</SearchLabel></template>
+							<option value="everyone">{{ i18n.ts._chat._chatAllowedUsers.everyone }}</option>
+							<option value="followers">{{ i18n.ts._chat._chatAllowedUsers.followers }}</option>
+							<option value="following">{{ i18n.ts._chat._chatAllowedUsers.following }}</option>
+							<option value="mutual">{{ i18n.ts._chat._chatAllowedUsers.mutual }}</option>
+							<option value="none">{{ i18n.ts._chat._chatAllowedUsers.none }}</option>
+							<template #caption>{{ i18n.ts._chat.chatAllowedUsers_note }}</template>
+						</MkSelect>
+					</SearchMarker>
+				</div>
+			</FormSection>
+		</SearchMarker>
 
 		<SearchMarker :keywords="['lockdown']">
 			<FormSection>
diff --git a/packages/frontend/src/router.definition.ts b/packages/frontend/src/router.definition.ts
index 23118160e2..d59b160b8b 100644
--- a/packages/frontend/src/router.definition.ts
+++ b/packages/frontend/src/router.definition.ts
@@ -16,6 +16,10 @@ export const page = (loader: AsyncComponentLoader) => defineAsyncComponent({
 	errorComponent: MkError,
 });
 
+function chatPage(...args: Parameters<typeof page>) {
+	return $i?.policies.chatAvailability !== 'unavailable' ? page(...args) : page(() => import('@/pages/not-found.vue'));
+}
+
 export const ROUTE_DEF = [{
 	path: '/@:username/pages/:pageName(*)',
 	component: page(() => import('@/pages/page.vue')),
@@ -42,19 +46,19 @@ export const ROUTE_DEF = [{
 	component: page(() => import('@/pages/clip.vue')),
 }, {
 	path: '/chat',
-	component: page(() => import('@/pages/chat/home.vue')),
+	component: chatPage(() => import('@/pages/chat/home.vue')),
 	loginRequired: true,
 }, {
 	path: '/chat/user/:userId',
-	component: page(() => import('@/pages/chat/room.vue')),
+	component: chatPage(() => import('@/pages/chat/room.vue')),
 	loginRequired: true,
 }, {
 	path: '/chat/room/:roomId',
-	component: page(() => import('@/pages/chat/room.vue')),
+	component: chatPage(() => import('@/pages/chat/room.vue')),
 	loginRequired: true,
 }, {
 	path: '/chat/messages/:messageId',
-	component: page(() => import('@/pages/chat/message.vue')),
+	component: chatPage(() => import('@/pages/chat/message.vue')),
 	loginRequired: true,
 }, {
 	path: '/instance-info/:host',
diff --git a/packages/frontend/src/utility/get-user-menu.ts b/packages/frontend/src/utility/get-user-menu.ts
index 8cf9f31d3e..563e45c446 100644
--- a/packages/frontend/src/utility/get-user-menu.ts
+++ b/packages/frontend/src/utility/get-user-menu.ts
@@ -364,7 +364,7 @@ export function getUserMenu(user: Misskey.entities.UserDetailed, router: Router
 			},
 		});
 
-		if ($i.policies.canChat && user.canChat && user.host == null) {
+		if ($i.policies.chatAvailability === 'available' && user.canChat && user.host == null) {
 			menuItems.push({
 				type: 'link',
 				icon: 'ti ti-messages',
diff --git a/packages/misskey-js/src/autogen/types.ts b/packages/misskey-js/src/autogen/types.ts
index 6bbf1e3319..6cc55507c0 100644
--- a/packages/misskey-js/src/autogen/types.ts
+++ b/packages/misskey-js/src/autogen/types.ts
@@ -5179,7 +5179,8 @@ export type components = {
       canImportFollowing: boolean;
       canImportMuting: boolean;
       canImportUserLists: boolean;
-      canChat: boolean;
+      /** @enum {string} */
+      chatAvailability: 'available' | 'readonly' | 'unavailable';
     };
     ReversiGameLite: {
       /** Format: id */