diff --git a/packages/backend/src/core/NoteCreateService.ts b/packages/backend/src/core/NoteCreateService.ts
index 4719735dfd..42d6aa4683 100644
--- a/packages/backend/src/core/NoteCreateService.ts
+++ b/packages/backend/src/core/NoteCreateService.ts
@@ -59,7 +59,6 @@ import { UtilityService } from '@/core/UtilityService.js';
 import { UserBlockingService } from '@/core/UserBlockingService.js';
 import { isReply } from '@/misc/is-reply.js';
 import { trackPromise } from '@/misc/promise-tracker.js';
-import { loadConfig } from '@/config.js';
 
 type NotificationType = 'reply' | 'renote' | 'quote' | 'mention';
 
@@ -321,6 +320,16 @@ export class NoteCreateService implements OnApplicationShutdown {
 			data.localOnly = true;
 		}
 
+		// デフォルトハッシュタグ処理
+		if (['public', 'home'].includes(data.visibility)) {
+			if (this.config.tagging.defaultTag != null) {
+				const tag = `#${this.config.tagging.defaultTag}`;
+				if (String(data.text).match(tag)) {
+					data.text = `${data.text}\n\n${tag}`;
+				}
+			}
+		}
+
 		if (data.text) {
 			if (data.text.length > DB_MAX_NOTE_TEXT_LENGTH) {
 				data.text = data.text.slice(0, DB_MAX_NOTE_TEXT_LENGTH);
@@ -915,11 +924,9 @@ export class NoteCreateService implements OnApplicationShutdown {
 			}
 
 			// デフォルトハッシュタグ
-			const config = loadConfig();
-			let defaultTag:string | null = config.tagging.defaultTag;
-			if (defaultTag != null) {
+			if (this.config.tagging.defaultTag != null) {
 				const noteTags = note.tags ? note.tags.map((t: string) => t.toLowerCase()) : [];
-				if (note.visibility === 'public' && noteTags.includes(normalizeForSearch(defaultTag))) {
+				if (note.visibility === 'public' && noteTags.includes(normalizeForSearch(this.config.tagging.defaultTag))) {
 					this.fanoutTimelineService.push('localTimelineWithReplies', note.id, 300, r);
 					this.fanoutTimelineService.push('localTimeline', note.id, 1000, r);
 					if (note.fileIds.length > 0) {
diff --git a/packages/backend/src/server/api/endpoints/notes/hybrid-timeline.ts b/packages/backend/src/server/api/endpoints/notes/hybrid-timeline.ts
index c6d6c55e9b..d328f4d846 100644
--- a/packages/backend/src/server/api/endpoints/notes/hybrid-timeline.ts
+++ b/packages/backend/src/server/api/endpoints/notes/hybrid-timeline.ts
@@ -201,7 +201,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				}
 
 				const config = loadConfig();
-				let defaultTag:string | null = config.tagging.defaultTag;
+				const defaultTag: string | null = config.tagging.defaultTag;
 				if (defaultTag == null) {
 					qb.orWhere('(note.visibility = \'public\') AND (note.userHost IS NULL)');
 				} else {
diff --git a/packages/backend/src/server/api/endpoints/notes/local-timeline.ts b/packages/backend/src/server/api/endpoints/notes/local-timeline.ts
index f4b962f465..24f8a303e8 100644
--- a/packages/backend/src/server/api/endpoints/notes/local-timeline.ts
+++ b/packages/backend/src/server/api/endpoints/notes/local-timeline.ts
@@ -152,7 +152,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		withReplies: boolean,
 	}, me: MiLocalUser | null) {
 		const config = loadConfig();
-		let defaultTag:string | null = config.tagging.defaultTag;
+		const defaultTag: string | null = config.tagging.defaultTag;
 		const query = this.queryService.makePaginationQuery(this.notesRepository.createQueryBuilder('note'),
 			ps.sinceId, ps.untilId)
 				.andWhere(new Brackets(qb => {
diff --git a/packages/backend/src/server/api/stream/channels/hybrid-timeline.ts b/packages/backend/src/server/api/stream/channels/hybrid-timeline.ts
index 29bdb8d327..dab99ba400 100644
--- a/packages/backend/src/server/api/stream/channels/hybrid-timeline.ts
+++ b/packages/backend/src/server/api/stream/channels/hybrid-timeline.ts
@@ -24,7 +24,7 @@ class HybridTimelineChannel extends Channel {
 	private withRenotes: boolean;
 	private withReplies: boolean;
 	private withFiles: boolean;
-	private defaultTag: string;
+	private defaultTag: string | null;
 
 	constructor(
 		private metaService: MetaService,
@@ -47,7 +47,7 @@ class HybridTimelineChannel extends Channel {
 		this.withReplies = params.withReplies ?? false;
 		this.withFiles = params.withFiles ?? false;
 		const config = loadConfig();
-		this.defaultTag =  config.tagging.defaultTag;
+		this.defaultTag = config.tagging.defaultTag;
 
 		// Subscribe events
 		this.subscriber.on('notesStream', this.onNote);
diff --git a/packages/backend/src/server/api/stream/channels/local-timeline.ts b/packages/backend/src/server/api/stream/channels/local-timeline.ts
index 00908b9164..e166af413d 100644
--- a/packages/backend/src/server/api/stream/channels/local-timeline.ts
+++ b/packages/backend/src/server/api/stream/channels/local-timeline.ts
@@ -22,7 +22,7 @@ class LocalTimelineChannel extends Channel {
 	private withRenotes: boolean;
 	private withReplies: boolean;
 	private withFiles: boolean;
-	private defaultTag: string;
+	private defaultTag: string | null;
 
 	constructor(
 		private metaService: MetaService,
@@ -45,7 +45,7 @@ class LocalTimelineChannel extends Channel {
 		this.withReplies = params.withReplies ?? false;
 		this.withFiles = params.withFiles ?? false;
 		const config = loadConfig();
-		this.defaultTag =  config.tagging.defaultTag;
+		this.defaultTag = config.tagging.defaultTag;
 
 		// Subscribe events
 		this.subscriber.on('notesStream', this.onNote);