diff --git a/packages/backend/src/services/add-note-to-antenna.ts b/packages/backend/src/services/add-note-to-antenna.ts
index 99bf1630d..b5bcd2304 100644
--- a/packages/backend/src/services/add-note-to-antenna.ts
+++ b/packages/backend/src/services/add-note-to-antenna.ts
@@ -6,7 +6,7 @@ import { isUserRelated } from '@/misc/is-user-related.js';
 import { publishAntennaStream, publishMainStream } from '@/services/stream.js';
 import { User } from '@/models/entities/user.js';
 
-export async function addNoteToAntenna(antenna: Antenna, note: Note, noteUser: { id: User['id']; }) {
+export async function addNoteToAntenna(antenna: Antenna, note: Note, noteUser: { id: User['id']; }): Promise<void> {
 	// 通知しない設定になっているか、自分自身の投稿なら既読にする
 	const read = !antenna.notify || (antenna.userId === noteUser.id);
 
diff --git a/packages/backend/src/services/create-notification.ts b/packages/backend/src/services/create-notification.ts
index 7b27c0261..ab4fbfa10 100644
--- a/packages/backend/src/services/create-notification.ts
+++ b/packages/backend/src/services/create-notification.ts
@@ -9,7 +9,7 @@ export async function createNotification(
 	notifieeId: User['id'],
 	type: Notification['type'],
 	data: Partial<Notification>,
-) {
+): Promise<Notification | null> {
 	if (data.notifierId && (notifieeId === data.notifierId)) {
 		return null;
 	}
diff --git a/packages/backend/src/services/fetch-instance-metadata.ts b/packages/backend/src/services/fetch-instance-metadata.ts
index d7f551d93..ad312c3c8 100644
--- a/packages/backend/src/services/fetch-instance-metadata.ts
+++ b/packages/backend/src/services/fetch-instance-metadata.ts
@@ -81,6 +81,7 @@ type NodeInfo = {
 		nodeName?: any;
 		nodeDescription?: any;
 		description?: any;
+		themeColor?: any;
 		maintainer?: {
 			name?: any;
 			email?: any;
@@ -125,7 +126,8 @@ async function fetchNodeinfo(instance: Instance): Promise<NodeInfo> {
 
 		return info as NodeInfo;
 	} catch (e) {
-		logger.error(`Failed to fetch nodeinfo of ${instance.host}: ${e.message}`);
+		const message = e instanceof Error ? e.message : e;
+		logger.error(`Failed to fetch nodeinfo of ${instance.host}: ${message}`);
 
 		throw e;
 	}
diff --git a/packages/backend/src/services/insert-moderation-log.ts b/packages/backend/src/services/insert-moderation-log.ts
index 821199962..6c225eb5b 100644
--- a/packages/backend/src/services/insert-moderation-log.ts
+++ b/packages/backend/src/services/insert-moderation-log.ts
@@ -2,7 +2,7 @@ import { ModerationLogs } from '@/models/index.js';
 import { genId } from '@/misc/gen-id.js';
 import { User } from '@/models/entities/user.js';
 
-export async function insertModerationLog(moderator: { id: User['id'] }, type: string, info?: Record<string, any>) {
+export async function insertModerationLog(moderator: { id: User['id'] }, type: string, info?: Record<string, any>): Promise<void> {
 	await ModerationLogs.insert({
 		id: genId(),
 		createdAt: new Date(),
diff --git a/packages/backend/src/services/push-notification.ts b/packages/backend/src/services/push-notification.ts
index e258c217a..6607c05d9 100644
--- a/packages/backend/src/services/push-notification.ts
+++ b/packages/backend/src/services/push-notification.ts
@@ -16,7 +16,7 @@ type pushNotificationsTypes = {
 };
 
 // Reduce the content of the push message because of the character limit
-function truncateNotification(notification: Packed<'Notification'>): any {
+function truncateNotification(notification: Packed<'Notification'>): Record<string, any> {
 	if (notification.note) {
 		return {
 			...notification,
@@ -37,7 +37,7 @@ function truncateNotification(notification: Packed<'Notification'>): any {
 	return notification;
 }
 
-export async function pushNotification<T extends keyof pushNotificationsTypes>(userId: string, type: T, body: pushNotificationsTypes[T]) {
+export async function pushNotification<T extends keyof pushNotificationsTypes>(userId: string, type: T, body: pushNotificationsTypes[T]): Promise<void> {
 	const meta = await fetchMeta();
 
 	// Register key pair information
diff --git a/packages/backend/src/services/relay.ts b/packages/backend/src/services/relay.ts
index 36bf88b9c..725ce30ce 100644
--- a/packages/backend/src/services/relay.ts
+++ b/packages/backend/src/services/relay.ts
@@ -36,7 +36,7 @@ export async function getRelayActor(): Promise<ILocalUser> {
 	return created as ILocalUser;
 }
 
-export async function addRelay(inbox: string) {
+export async function addRelay(inbox: string): Promise<Relay> {
 	const relay = await Relays.insert({
 		id: genId(),
 		inbox,
@@ -51,7 +51,7 @@ export async function addRelay(inbox: string) {
 	return relay;
 }
 
-export async function removeRelay(inbox: string) {
+export async function removeRelay(inbox: string): Promise<void> {
 	const relay = await Relays.findOneBy({
 		inbox,
 	});
@@ -69,12 +69,12 @@ export async function removeRelay(inbox: string) {
 	await Relays.delete(relay.id);
 }
 
-export async function listRelay() {
+export async function listRelay(): Promise<Relay[]> {
 	const relays = await Relays.find();
 	return relays;
 }
 
-export async function relayAccepted(id: string) {
+export async function relayAccepted(id: string): Promise<string> {
 	const result = await Relays.update(id, {
 		status: 'accepted',
 	});
@@ -82,7 +82,7 @@ export async function relayAccepted(id: string) {
 	return JSON.stringify(result);
 }
 
-export async function relayRejected(id: string) {
+export async function relayRejected(id: string): Promise<string> {
 	const result = await Relays.update(id, {
 		status: 'rejected',
 	});
@@ -90,11 +90,11 @@ export async function relayRejected(id: string) {
 	return JSON.stringify(result);
 }
 
-export async function deliverToRelays(user: { id: User['id']; host: null; }, activity: any) {
+export async function deliverToRelays(user: { id: User['id']; host: null; }, activity: any): Promise<void> {
 	if (activity == null) return;
 
 	const relays = await relaysCache.fetch(null);
-	if (relays.length === 0) return;
+	if (relays == null || relays.length === 0) return;
 
 	// TODO
 	//const copy = structuredClone(activity);
diff --git a/packages/backend/src/services/unsuspend-user.ts b/packages/backend/src/services/unsuspend-user.ts
index 3ed7ce850..766b10f21 100644
--- a/packages/backend/src/services/unsuspend-user.ts
+++ b/packages/backend/src/services/unsuspend-user.ts
@@ -8,7 +8,7 @@ import { User } from '@/models/entities/user.js';
 import { Users, Followings } from '@/models/index.js';
 import { publishInternalEvent } from '@/services/stream.js';
 
-export async function doPostUnsuspend(user: User) {
+export async function doPostUnsuspend(user: User): Promise<void> {
 	publishInternalEvent('userChangeSuspendedState', { id: user.id, isSuspended: false });
 
 	if (Users.isLocalUser(user)) {
diff --git a/packages/backend/src/services/update-hashtag.ts b/packages/backend/src/services/update-hashtag.ts
index 9f549c3f4..7a77cb124 100644
--- a/packages/backend/src/services/update-hashtag.ts
+++ b/packages/backend/src/services/update-hashtag.ts
@@ -16,7 +16,7 @@ export async function updateUsertags(user: User, tags: string[]): Promise<void>
 		await updateHashtag(user, tag, true, true);
 	}
 
-	for (const tag of (user.tags || []).filter(x => !tags.includes(x))) {
+	for (const tag of user.tags.filter(x => !tags.includes(x))) {
 		await updateHashtag(user, tag, true, false);
 	}
 }
diff --git a/packages/backend/src/services/user-cache.ts b/packages/backend/src/services/user-cache.ts
index d30b76a24..d67931c2c 100644
--- a/packages/backend/src/services/user-cache.ts
+++ b/packages/backend/src/services/user-cache.ts
@@ -1,3 +1,4 @@
+import { IsNull } from 'typeorm';
 import { CacheableLocalUser, CacheableUser, ILocalUser } from '@/models/entities/user.js';
 import { Users } from '@/models/index.js';
 import { Cache } from '@/misc/cache.js';
@@ -5,15 +6,15 @@ import { subscriber } from '@/db/redis.js';
 
 export const userByIdCache = new Cache<CacheableUser>(
 	Infinity,
-	(id) => Users.findOneBy({ id }).then(x => x ?? undefined),
+	async (id) => id ? (await Users.findOneBy({ id }) ?? undefined) : undefined,
 );
 export const localUserByNativeTokenCache = new Cache<CacheableLocalUser>(
 	Infinity,
-	(token) => Users.findOneBy({ token }).then(x => x ?? undefined),
+	async (token) => token ? (await Users.findOneBy({ token, host: IsNull() }) as ILocalUser | null ?? undefined) : undefined,
 );
 export const uriPersonCache = new Cache<CacheableUser>(
 	Infinity,
-	(uri) => Users.findOneBy({ uri }).then(x => x ?? undefined),
+	async (uri) => uri ? (await Users.findOneBy({ uri }) ?? undefined) : undefined,
 );
 
 subscriber.on('message', async (_, data) => {