diff --git a/packages/frontend/src/pages/chat/XMessage.vue b/packages/frontend/src/pages/chat/XMessage.vue
index 33741b1845..b1be8d5fd4 100644
--- a/packages/frontend/src/pages/chat/XMessage.vue
+++ b/packages/frontend/src/pages/chat/XMessage.vue
@@ -5,33 +5,28 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <template>
 <div :class="[$style.root, { [$style.isMe]: isMe }]">
-	<MkAvatar :class="$style.avatar" :user="message.fromUser" :link="!isMe" :preview="false"/>
+	<MkAvatar :class="$style.avatar" :user="message.fromUser!" :link="!isMe" :preview="false"/>
 	<div :class="$style.body" @contextmenu.stop="onContextmenu">
-		<div :class="$style.header"><MkUserName v-if="!isMe && prefer.s['chat.showSenderName']" :user="message.fromUser"/></div>
+		<div :class="$style.header"><MkUserName v-if="!isMe && prefer.s['chat.showSenderName'] && message.fromUser != null" :user="message.fromUser"/></div>
 		<MkFukidashi :class="$style.fukidashi" :tail="isMe ? 'right' : 'left'" :accented="isMe">
-			<div v-if="!message.isDeleted" :class="$style.content">
-				<Mfm
-					v-if="message.text"
-					ref="text"
-					class="_selectable"
-					:text="message.text"
-					:i="$i"
-					:nyaize="'respect'"
-					:enableEmojiMenu="true"
-					:enableEmojiMenuReaction="true"
-				/>
-				<MkMediaList v-if="message.file" :mediaList="[message.file]" :class="$style.file"/>
-			</div>
-			<div v-else :class="$style.content">
-				<p>{{ i18n.ts.deleted }}</p>
-			</div>
+			<Mfm
+				v-if="message.text"
+				ref="text"
+				class="_selectable"
+				:text="message.text"
+				:i="$i"
+				:nyaize="'respect'"
+				:enableEmojiMenu="true"
+				:enableEmojiMenuReaction="true"
+			/>
+			<MkMediaList v-if="message.file" :mediaList="[message.file]" :class="$style.file"/>
 		</MkFukidashi>
 		<MkUrlPreview v-for="url in urls" :key="url" :url="url" style="margin: 8px 0;"/>
 		<div :class="$style.footer">
 			<button class="_textButton" style="color: currentColor;" @click="showMenu"><i class="ti ti-dots-circle-horizontal"></i></button>
 			<MkTime :class="$style.time" :time="message.createdAt"/>
-			<MkA v-if="isSearchResult && message.toRoomId" :to="`/chat/room/${message.toRoomId}`">{{ message.toRoom.name }}</MkA>
-			<MkA v-if="isSearchResult && message.toUserId && isMe" :to="`/chat/user/${message.toUserId}`">@{{ message.toUser.username }}</MkA>
+			<MkA v-if="isSearchResult && 'toRoom' in message && message.toRoom != null" :to="`/chat/room/${message.toRoomId}`">{{ message.toRoom?.name }}</MkA>
+			<MkA v-if="isSearchResult && 'toUser' in message && message.toUser != null && isMe" :to="`/chat/user/${message.toUserId}`">@{{ message.toUser?.username }}</MkA>
 		</div>
 		<TransitionGroup
 			:enterActiveClass="prefer.s.animation ? $style.transition_reaction_enterActive : ''"
@@ -41,8 +36,8 @@ SPDX-License-Identifier: AGPL-3.0-only
 			:moveClass="prefer.s.animation ? $style.transition_reaction_move : ''"
 			tag="div" :class="$style.reactions"
 		>
-			<div v-for="record in message.reactions" :key="record.reaction + record.user.id" :class="[$style.reaction, record.user.id === $i.id ? $style.reactionMy : null]" @click="onReactionClick(record)">
-				<MkAvatar :user="record.user" :link="false" :class="$style.reactionAvatar"/>
+			<div v-for="record in message.reactions" :key="record.reaction + record.user?.id" :class="[$style.reaction, record.user?.id === $i.id ? $style.reactionMy : null]" @click="onReactionClick(record)">
+				<MkAvatar :user="record.user!" :link="false" :class="$style.reactionAvatar"/>
 				<MkReactionIcon
 					:withTooltip="true"
 					:reaction="record.reaction.replace(/^:(\w+):$/, ':$1@.:')"
@@ -76,6 +71,7 @@ import * as sound from '@/utility/sound.js';
 import MkReactionIcon from '@/components/MkReactionIcon.vue';
 import { prefer } from '@/preferences.js';
 import { DI } from '@/di.js';
+import { getHTMLElementOrNull } from '@/utility/get-dom-node-or-null.js';
 
 const $i = ensureSignin();
 
@@ -88,6 +84,8 @@ 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;
+
 	sound.playMisskeySfx('reaction');
 	misskeyApi('chat/messages/react', {
 		messageId: props.message.id,
@@ -96,7 +94,12 @@ provide(DI.mfmEmojiReactCallback, (reaction) => {
 });
 
 function react(ev: MouseEvent) {
-	reactionPicker.show(ev.currentTarget ?? ev.target, null, async (reaction) => {
+	if (!$i.policies.canChat) return;
+
+	const targetEl = getHTMLElementOrNull(ev.currentTarget ?? ev.target);
+	if (!targetEl) return;
+
+	reactionPicker.show(targetEl, null, async (reaction) => {
 		sound.playMisskeySfx('reaction');
 		misskeyApi('chat/messages/react', {
 			messageId: props.message.id,
@@ -106,13 +109,15 @@ function react(ev: MouseEvent) {
 }
 
 function onReactionClick(record: Misskey.entities.ChatMessage['reactions'][0]) {
-	if (record.user.id === $i.id) {
+	if (!$i.policies.canChat) return;
+
+	if (record.user?.id === $i.id) {
 		misskeyApi('chat/messages/unreact', {
 			messageId: props.message.id,
 			reaction: record.reaction,
 		});
 	} else {
-		if (!props.message.reactions.some(r => r.user.id === $i.id && r.reaction === record.reaction)) {
+		if (!props.message.reactions.some(r => r.user?.id === $i.id && r.reaction === record.reaction)) {
 			sound.playMisskeySfx('reaction');
 			misskeyApi('chat/messages/react', {
 				messageId: props.message.id,
@@ -132,7 +137,7 @@ function onContextmenu(ev: MouseEvent) {
 function showMenu(ev: MouseEvent, contextmenu = false) {
 	const menu: MenuItem[] = [];
 
-	if (!isMe.value) {
+	if (!isMe.value && $i.policies.canChat) {
 		menu.push({
 			text: i18n.ts.reaction,
 			icon: 'ti ti-mood-plus',
@@ -150,7 +155,7 @@ function showMenu(ev: MouseEvent, contextmenu = false) {
 		text: i18n.ts.copyContent,
 		icon: 'ti ti-copy',
 		action: () => {
-			copyToClipboard(props.message.text);
+			copyToClipboard(props.message.text ?? '');
 		},
 	});
 
@@ -158,7 +163,7 @@ function showMenu(ev: MouseEvent, contextmenu = false) {
 		type: 'divider',
 	});
 
-	if (isMe.value) {
+	if (isMe.value && $i.policies.canChat) {
 		menu.push({
 			text: i18n.ts.delete,
 			icon: 'ti ti-trash',
@@ -169,14 +174,16 @@ function showMenu(ev: MouseEvent, contextmenu = false) {
 				});
 			},
 		});
-	} else {
+	}
+
+	if (!isMe.value && props.message.fromUser != null) {
 		menu.push({
 			text: i18n.ts.reportAbuse,
 			icon: 'ti ti-exclamation-circle',
 			action: () => {
 				const localUrl = `${url}/chat/messages/${props.message.id}`;
 				const { dispose } = os.popup(defineAsyncComponent(() => import('@/components/MkAbuseReportWindow.vue')), {
-					user: props.message.fromUser,
+					user: props.message.fromUser!,
 					initialComment: `${localUrl}\n-----\n`,
 				}, {
 					closed: () => dispose(),
diff --git a/packages/frontend/src/pages/chat/home.home.vue b/packages/frontend/src/pages/chat/home.home.vue
index 105f5f7989..17f0e0fbcd 100644
--- a/packages/frontend/src/pages/chat/home.home.vue
+++ b/packages/frontend/src/pages/chat/home.home.vue
@@ -67,7 +67,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
-import { computed, onActivated, onDeactivated, onMounted, ref } from 'vue';
+import { onActivated, onDeactivated, onMounted, ref } from 'vue';
 import * as Misskey from 'misskey-js';
 import { useInterval } from '@@/js/use-interval.js';
 import XMessage from './XMessage.vue';
@@ -163,7 +163,7 @@ async function fetchHistory() {
 		.map(m => ({
 			id: m.id,
 			message: m,
-			other: m.room == null ? (m.fromUserId === $i.id ? m.toUser : m.fromUser) : null,
+			other: (!('room' in m) || m.room == null) ? (m.fromUserId === $i.id ? m.toUser : m.fromUser) : null,
 			isMe: m.fromUserId === $i.id,
 		}));
 
diff --git a/packages/frontend/src/pages/chat/home.invitations.vue b/packages/frontend/src/pages/chat/home.invitations.vue
index 4c3c0b282e..82b22ea9dd 100644
--- a/packages/frontend/src/pages/chat/home.invitations.vue
+++ b/packages/frontend/src/pages/chat/home.invitations.vue
@@ -35,18 +35,14 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
-import { computed, onMounted, ref } from 'vue';
+import { onMounted, ref } from 'vue';
 import * as Misskey from 'misskey-js';
 import MkButton from '@/components/MkButton.vue';
 import { i18n } from '@/i18n.js';
 import { misskeyApi } from '@/utility/misskey-api.js';
-import { ensureSignin } from '@/i.js';
 import { useRouter } from '@/router.js';
-import * as os from '@/os.js';
 import MkFolder from '@/components/MkFolder.vue';
 
-const $i = ensureSignin();
-
 const router = useRouter();
 
 const fetching = ref(true);
@@ -55,8 +51,7 @@ const invitations = ref<Misskey.entities.ChatRoomInvitation[]>([]);
 async function fetchInvitations() {
 	fetching.value = true;
 
-	const res = await misskeyApi('chat/rooms/invitations/inbox', {
-	});
+	const res = await misskeyApi('chat/rooms/invitations/inbox');
 
 	invitations.value = res;
 
diff --git a/packages/frontend/src/pages/chat/home.joiningRooms.vue b/packages/frontend/src/pages/chat/home.joiningRooms.vue
index 63e4d2adf8..f9fd6bfd55 100644
--- a/packages/frontend/src/pages/chat/home.joiningRooms.vue
+++ b/packages/frontend/src/pages/chat/home.joiningRooms.vue
@@ -6,7 +6,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 <template>
 <div class="_gaps">
 	<div v-if="memberships.length > 0" class="_gaps_s">
-		<XRoom v-for="membership in memberships" :key="membership.id" :room="membership.room"/>
+		<XRoom v-for="membership in memberships" :key="membership.id" :room="membership.room!"/>
 	</div>
 	<div v-if="!fetching && memberships.length == 0" class="_fullinfo">
 		<div>{{ i18n.ts._chat.noRooms }}</div>
@@ -16,19 +16,11 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
-import { computed, onMounted, ref } from 'vue';
+import { onMounted, ref } from 'vue';
 import * as Misskey from 'misskey-js';
 import XRoom from './XRoom.vue';
-import MkButton from '@/components/MkButton.vue';
 import { i18n } from '@/i18n.js';
 import { misskeyApi } from '@/utility/misskey-api.js';
-import { ensureSignin } from '@/i.js';
-import { useRouter } from '@/router.js';
-import * as os from '@/os.js';
-
-const $i = ensureSignin();
-
-const router = useRouter();
 
 const fetching = ref(true);
 const memberships = ref<Misskey.entities.ChatRoomMembership[]>([]);
@@ -36,8 +28,7 @@ const memberships = ref<Misskey.entities.ChatRoomMembership[]>([]);
 async function fetchRooms() {
 	fetching.value = true;
 
-	const res = await misskeyApi('chat/rooms/joining', {
-	});
+	const res = await misskeyApi('chat/rooms/joining');
 
 	memberships.value = res;
 
diff --git a/packages/frontend/src/pages/chat/home.ownedRooms.vue b/packages/frontend/src/pages/chat/home.ownedRooms.vue
index b0449fb373..ce7da15563 100644
--- a/packages/frontend/src/pages/chat/home.ownedRooms.vue
+++ b/packages/frontend/src/pages/chat/home.ownedRooms.vue
@@ -16,19 +16,11 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
-import { computed, onMounted, ref } from 'vue';
+import { onMounted, ref } from 'vue';
 import * as Misskey from 'misskey-js';
 import XRoom from './XRoom.vue';
-import MkButton from '@/components/MkButton.vue';
 import { i18n } from '@/i18n.js';
 import { misskeyApi } from '@/utility/misskey-api.js';
-import { ensureSignin } from '@/i.js';
-import { useRouter } from '@/router.js';
-import * as os from '@/os.js';
-
-const $i = ensureSignin();
-
-const router = useRouter();
 
 const fetching = ref(true);
 const rooms = ref<Misskey.entities.ChatRoom[]>([]);
diff --git a/packages/frontend/src/pages/chat/home.vue b/packages/frontend/src/pages/chat/home.vue
index 9bb7235a64..e29ab28f2d 100644
--- a/packages/frontend/src/pages/chat/home.vue
+++ b/packages/frontend/src/pages/chat/home.vue
@@ -18,7 +18,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
-import { computed, onMounted, ref } from 'vue';
+import { computed, ref } from 'vue';
 import XHome from './home.home.vue';
 import XInvitations from './home.invitations.vue';
 import XJoiningRooms from './home.joiningRooms.vue';
diff --git a/packages/frontend/src/pages/chat/message.vue b/packages/frontend/src/pages/chat/message.vue
index 975d1a2be9..3ac90a93fd 100644
--- a/packages/frontend/src/pages/chat/message.vue
+++ b/packages/frontend/src/pages/chat/message.vue
@@ -6,7 +6,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 <template>
 <PageWithHeader>
 	<MkSpacer :contentMax="700">
-		<div v-if="initializing">
+		<div v-if="initializing || message == null">
 			<MkLoading/>
 		</div>
 		<div v-else>
@@ -17,23 +17,19 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
-import { ref, useTemplateRef, computed, watch, onMounted, nextTick, onBeforeUnmount, onDeactivated, onActivated } from 'vue';
+import { ref, onMounted } from 'vue';
 import * as Misskey from 'misskey-js';
 import XMessage from './XMessage.vue';
-import * as os from '@/os.js';
-import { useStream } from '@/stream.js';
 import { i18n } from '@/i18n.js';
-import { ensureSignin } from '@/i.js';
 import { misskeyApi } from '@/utility/misskey-api.js';
 import { definePage } from '@/page.js';
-import MkButton from '@/components/MkButton.vue';
 
 const props = defineProps<{
 	messageId?: string;
 }>();
 
 const initializing = ref(true);
-const message = ref<Misskey.entities.ChatMessage>();
+const message = ref<Misskey.entities.ChatMessage | null>();
 
 async function initialize() {
 	initializing.value = true;
diff --git a/packages/frontend/src/pages/chat/room.form.vue b/packages/frontend/src/pages/chat/room.form.vue
index 27ddbeb565..d8fe920d1a 100644
--- a/packages/frontend/src/pages/chat/room.form.vue
+++ b/packages/frontend/src/pages/chat/room.form.vue
@@ -34,14 +34,12 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
-import { onMounted, watch, ref, shallowRef, computed, nextTick, readonly } from 'vue';
+import { onMounted, watch, ref, shallowRef, computed, nextTick, readonly, onBeforeUnmount } from 'vue';
 import * as Misskey from 'misskey-js';
 //import insertTextAtCursor from 'insert-text-at-cursor';
-import { throttle } from 'throttle-debounce';
 import { formatTimeString } from '@/utility/format-time-string.js';
 import { selectFile } from '@/utility/select-file.js';
 import * as os from '@/os.js';
-import { useStream } from '@/stream.js';
 import { i18n } from '@/i18n.js';
 import { uploadFile } from '@/utility/upload.js';
 import { miLocalStorage } from '@/local-storage.js';
@@ -62,6 +60,7 @@ const text = ref<string>('');
 const file = ref<Misskey.entities.DriveFile | null>(null);
 const sending = ref(false);
 const textareaReadOnly = ref(false);
+let autocompleteInstance: Autocomplete | null = null;
 
 const canSend = computed(() => (text.value != null && text.value !== '') || file.value != null);
 
@@ -171,7 +170,9 @@ function chooseFile(ev: MouseEvent) {
 }
 
 function onChangeFile() {
-	if (fileEl.value.files![0]) upload(fileEl.value.files[0]);
+	if (fileEl.value == null || fileEl.value.files == null) return;
+
+	if (fileEl.value.files[0]) upload(fileEl.value.files[0]);
 }
 
 function upload(fileToUpload: File, name?: string) {
@@ -270,8 +271,9 @@ async function insertEmoji(ev: MouseEvent) {
 }
 
 onMounted(() => {
-	// TODO: detach when unmount
-	new Autocomplete(textareaEl.value, text);
+	if (textareaEl.value != null) {
+		autocompleteInstance = new Autocomplete(textareaEl.value, text);
+	}
 
 	// 書きかけの投稿を復元
 	const draft = JSON.parse(miLocalStorage.getItem('chatMessageDrafts') || '{}')[getDraftKey()];
@@ -280,6 +282,13 @@ onMounted(() => {
 		file.value = draft.data.file;
 	}
 });
+
+onBeforeUnmount(() => {
+	if (autocompleteInstance) {
+		autocompleteInstance.detach();
+		autocompleteInstance = null;
+	}
+})
 </script>
 
 <style lang="scss" module>
diff --git a/packages/frontend/src/pages/chat/room.info.vue b/packages/frontend/src/pages/chat/room.info.vue
index 8439e5f772..2f091388a0 100644
--- a/packages/frontend/src/pages/chat/room.info.vue
+++ b/packages/frontend/src/pages/chat/room.info.vue
@@ -26,11 +26,10 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
-import { computed, onMounted, ref, watch } from 'vue';
+import { computed, ref, watch } from 'vue';
 import * as Misskey from 'misskey-js';
 import MkButton from '@/components/MkButton.vue';
 import { i18n } from '@/i18n.js';
-import { misskeyApi } from '@/utility/misskey-api.js';
 import * as os from '@/os.js';
 import { ensureSignin } from '@/i.js';
 import MkInput from '@/components/MkInput.vue';
@@ -73,7 +72,7 @@ async function del() {
 	router.push('/chat');
 }
 
-const isMuted = ref(props.room.isMuted);
+const isMuted = ref(props.room.isMuted ?? false);
 
 watch(isMuted, async () => {
 	await os.apiWithDialog('chat/rooms/mute', {
diff --git a/packages/frontend/src/pages/chat/room.members.vue b/packages/frontend/src/pages/chat/room.members.vue
index bff038570f..80e387d179 100644
--- a/packages/frontend/src/pages/chat/room.members.vue
+++ b/packages/frontend/src/pages/chat/room.members.vue
@@ -14,7 +14,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 	<hr v-if="memberships.length > 0">
 
 	<div v-for="membership in memberships" :key="membership.id" :class="$style.membership">
-		<MkA :class="$style.membershipBody" :to="`${userPage(membership.user)}`">
+		<MkA v-if="membership.user != null" :class="$style.membershipBody" :to="`${userPage(membership.user)}`">
 			<MkUserCardMini :user="membership.user"/>
 		</MkA>
 	</div>
@@ -39,7 +39,6 @@ import * as Misskey from 'misskey-js';
 import MkButton from '@/components/MkButton.vue';
 import { i18n } from '@/i18n.js';
 import { misskeyApi } from '@/utility/misskey-api.js';
-import * as os from '@/os.js';
 import MkUserCardMini from '@/components/MkUserCardMini.vue';
 import { userPage } from '@/filters/user.js';
 import { ensureSignin } from '@/i.js';
diff --git a/packages/frontend/src/pages/chat/room.search.vue b/packages/frontend/src/pages/chat/room.search.vue
index e382834578..20b6e22a46 100644
--- a/packages/frontend/src/pages/chat/room.search.vue
+++ b/packages/frontend/src/pages/chat/room.search.vue
@@ -33,14 +33,13 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
-import { computed, onMounted, ref } from 'vue';
+import { ref } from 'vue';
 import * as Misskey from 'misskey-js';
 import XMessage from './XMessage.vue';
 import MkButton from '@/components/MkButton.vue';
 import { i18n } from '@/i18n.js';
 import { infoImageUrl } from '@/instance.js';
 import { misskeyApi } from '@/utility/misskey-api.js';
-import * as os from '@/os.js';
 import MkInput from '@/components/MkInput.vue';
 import MkFoldableSection from '@/components/MkFoldableSection.vue';
 
diff --git a/packages/frontend/src/pages/chat/room.vue b/packages/frontend/src/pages/chat/room.vue
index ce823968f7..a8be4879cd 100644
--- a/packages/frontend/src/pages/chat/room.vue
+++ b/packages/frontend/src/pages/chat/room.vue
@@ -79,15 +79,16 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
-import { ref, useTemplateRef, computed, watch, onMounted, nextTick, onBeforeUnmount, onDeactivated, onActivated } from 'vue';
+import { ref, useTemplateRef, computed, onMounted, onBeforeUnmount, onDeactivated, onActivated } from 'vue';
 import * as Misskey from 'misskey-js';
-import { getScrollContainer, isTailVisible } from '@@/js/scroll.js';
+import { getScrollContainer } from '@@/js/scroll.js';
 import XMessage from './XMessage.vue';
 import XForm from './room.form.vue';
 import XSearch from './room.search.vue';
 import XMembers from './room.members.vue';
 import XInfo from './room.info.vue';
 import type { MenuItem } from '@/types/menu.js';
+import type { PageHeaderItem } from '@/types/page-header.js';
 import * as os from '@/os.js';
 import { useStream } from '@/stream.js';
 import * as sound from '@/utility/sound.js';
@@ -109,13 +110,20 @@ const props = defineProps<{
 	roomId?: string;
 }>();
 
+type NormalizedChatMessage = Omit<Misskey.entities.ChatMessageLite, 'fromUser' | 'reactions'> & {
+	fromUser: Misskey.entities.UserLite;
+	reactions: (Misskey.entities.ChatMessageLite['reactions'][number] & {
+		user: Misskey.entities.UserLite;
+	})[];
+};
+
 const initializing = ref(true);
 const moreFetching = ref(false);
-const messages = ref<Misskey.entities.ChatMessage[]>([]);
+const messages = ref<NormalizedChatMessage[]>([]);
 const canFetchMore = ref(false);
 const user = ref<Misskey.entities.UserDetailed | null>(null);
 const room = ref<Misskey.entities.ChatRoom | null>(null);
-const connection = ref<Misskey.ChannelConnection<Misskey.Channels['chatUser'] | Misskey.Channels['chatRoom']> | null>(null);
+const connection = ref<Misskey.IChannelConnection<Misskey.Channels['chatUser']> | Misskey.IChannelConnection<Misskey.Channels['chatRoom']> | null>(null);
 const showIndicator = ref(false);
 const timelineEl = useTemplateRef('timelineEl');
 
@@ -138,7 +146,7 @@ useMutationObserver(timelineEl, {
 	}
 });
 
-function normalizeMessage(message: Misskey.entities.ChatMessageLite | Misskey.entities.ChatMessage) {
+function normalizeMessage(message: Misskey.entities.ChatMessageLite | Misskey.entities.ChatMessage): NormalizedChatMessage {
 	const reactions = [...message.reactions];
 	for (const record of reactions) {
 		if (room.value == null && record.user == null) { // 1on1の時はuserは省略される
@@ -148,8 +156,11 @@ function normalizeMessage(message: Misskey.entities.ChatMessageLite | Misskey.en
 
 	return {
 		...message,
-		fromUser: message.fromUser ?? (message.fromUserId === $i.id ? $i : user),
-		reactions,
+		fromUser: message.fromUser ?? (message.fromUserId === $i.id ? $i : user.value!),
+		reactions: reactions.map(record => ({
+			...record,
+			user: record.user ?? (message.fromUserId === $i.id ? user.value! : $i),
+		})),
 	};
 }
 
@@ -174,18 +185,18 @@ async function initialize() {
 		connection.value = useStream().useChannel('chatUser', {
 			otherId: user.value.id,
 		});
-		connection.value.on('message', onMessage);
-		connection.value.on('deleted', onDeleted);
-		connection.value.on('react', onReact);
-		connection.value.on('unreact', onUnreact);
+		connection.value?.on('message', onMessage);
+		connection.value?.on('deleted', onDeleted);
+		connection.value?.on('react', onReact);
+		connection.value?.on('unreact', onUnreact);
 	} else {
 		const [r, m] = await Promise.all([
 			misskeyApi('chat/rooms/show', { roomId: props.roomId }),
 			misskeyApi('chat/messages/room-timeline', { roomId: props.roomId, limit: LIMIT }),
 		]);
 
-		room.value = r;
-		messages.value = m.map(x => normalizeMessage(x));
+		room.value = r as Misskey.entities.ChatRoomsShowResponse;
+		messages.value = (m as Misskey.entities.ChatMessagesRoomTimelineResponse).map(x => normalizeMessage(x));
 
 		if (messages.value.length === LIMIT) {
 			canFetchMore.value = true;
@@ -221,11 +232,11 @@ async function fetchMore() {
 	moreFetching.value = true;
 
 	const newMessages = props.userId ? await misskeyApi('chat/messages/user-timeline', {
-		userId: user.value.id,
+		userId: user.value!.id,
 		limit: LIMIT,
 		untilId: messages.value[messages.value.length - 1].id,
 	}) : await misskeyApi('chat/messages/room-timeline', {
-		roomId: room.value.id,
+		roomId: room.value!.id,
 		limit: LIMIT,
 		untilId: messages.value[messages.value.length - 1].id,
 	});
@@ -236,7 +247,7 @@ async function fetchMore() {
 	moreFetching.value = false;
 }
 
-function onMessage(message: Misskey.entities.ChatMessage) {
+function onMessage(message: Misskey.entities.ChatMessageLite) {
 	sound.playMisskeySfx('chatMessage');
 
 	messages.value.unshift(normalizeMessage(message));
@@ -253,22 +264,22 @@ function onMessage(message: Misskey.entities.ChatMessage) {
 	}
 }
 
-function onDeleted(id) {
+function onDeleted(id: string) {
 	const index = messages.value.findIndex(m => m.id === id);
 	if (index !== -1) {
 		messages.value.splice(index, 1);
 	}
 }
 
-function onReact(ctx) {
+function onReact(ctx: Parameters<Misskey.Channels['chatUser']['events']['react']>[0] | Parameters<Misskey.Channels['chatRoom']['events']['react']>[0]) {
 	const message = messages.value.find(m => m.id === ctx.messageId);
 	if (message) {
 		if (room.value == null) { // 1on1の時はuserは省略される
 			message.reactions.push({
 				reaction: ctx.reaction,
-				user: message.fromUserId === $i.id ? user : $i,
+				user: message.fromUserId === $i.id ? user.value! : $i,
 			});
-		} else {
+		} else if (ctx.user != null) {
 			message.reactions.push({
 				reaction: ctx.reaction,
 				user: ctx.user,
@@ -277,10 +288,10 @@ function onReact(ctx) {
 	}
 }
 
-function onUnreact(ctx) {
+function onUnreact(ctx: Parameters<Misskey.Channels['chatUser']['events']['unreact']>[0] | Parameters<Misskey.Channels['chatRoom']['events']['unreact']>[0]) {
 	const message = messages.value.find(m => m.id === ctx.messageId);
-	if (message) {
-		const index = message.reactions.findIndex(r => r.reaction === ctx.reaction && r.user.id === ctx.user.id);
+	if (message && ctx.user != null) {
+		const index = message.reactions.findIndex(r => r.reaction === ctx.reaction && r.user.id === ctx.user!.id);
 		if (index !== -1) {
 			message.reactions.splice(index, 1);
 		}
@@ -310,6 +321,8 @@ onBeforeUnmount(() => {
 });
 
 async function inviteUser() {
+	if (room.value == null) return;
+
 	const invitee = await os.selectUser({ includeSelf: false, localOnly: true });
 	os.apiWithDialog('chat/rooms/invitations/create', {
 		roomId: room.value?.id,
@@ -384,19 +397,36 @@ const headerTabs = computed(() => room.value ? [{
 	icon: 'ti ti-search',
 }]);
 
-const headerActions = computed(() => [{
+const headerActions = computed<PageHeaderItem[]>(() => [{
 	icon: 'ti ti-dots',
+	text: '',
 	handler: showMenu,
 }]);
 
-definePage(computed(() => !initializing.value ? user.value ? {
-	userName: user,
-	title: user.value.name ?? user.value.username,
-	avatar: user,
-} : {
-	title: room.value?.name,
-	icon: 'ti ti-users',
-} : null));
+definePage(computed(() => {
+	if (!initializing.value) {
+		if (user.value) {
+			return {
+				userName: user.value,
+				title: user.value.name ?? user.value.username,
+				avatar: user.value,
+			};
+		} else if (room.value) {
+			return {
+				title: room.value.name,
+				icon: 'ti ti-users',
+			};
+		} else {
+			return {
+				title: i18n.ts.chat,
+			};
+		}
+	} else {
+		return {
+			title: i18n.ts.chat,
+		};
+	}
+}));
 </script>
 
 <style lang="scss" module>
diff --git a/packages/frontend/src/use/use-mutation-observer.ts b/packages/frontend/src/use/use-mutation-observer.ts
index b35dbcd7a8..7b774022dc 100644
--- a/packages/frontend/src/use/use-mutation-observer.ts
+++ b/packages/frontend/src/use/use-mutation-observer.ts
@@ -4,9 +4,9 @@
  */
 
 import { onUnmounted, watch } from 'vue';
-import type { Ref, ShallowRef } from 'vue';
+import type { Ref } from 'vue';
 
-export function useMutationObserver(targetNodeRef: Ref<HTMLElement | undefined>, options: MutationObserverInit, callback: MutationCallback): void {
+export function useMutationObserver(targetNodeRef: Ref<HTMLElement | null | undefined>, options: MutationObserverInit, callback: MutationCallback): void {
 	const observer = new MutationObserver(callback);
 
 	watch(targetNodeRef, (targetNode) => {