diff --git a/packages/backend/src/server/web/ClientServerService.ts b/packages/backend/src/server/web/ClientServerService.ts
index cd1df1605c..3ed811e737 100644
--- a/packages/backend/src/server/web/ClientServerService.ts
+++ b/packages/backend/src/server/web/ClientServerService.ts
@@ -323,19 +323,16 @@ export class ClientServerService {
 				done();
 			});
 		} else {
-			const configUrl = new URL(this.config.url);
-			const urlOriginWithoutPort = configUrl.origin.replace(/:\d+$/, '');
-
 			const port = (process.env.VITE_PORT ?? '5173');
 			fastify.register(fastifyProxy, {
-				upstream: urlOriginWithoutPort + ':' + port,
+				upstream: `http://localhost:${port}`,
 				prefix: '/vite',
 				rewritePrefix: '/vite',
 			});
 
 			const embedPort = (process.env.EMBED_VITE_PORT ?? '5174');
 			fastify.register(fastifyProxy, {
-				upstream: urlOriginWithoutPort + ':' + embedPort,
+				upstream: `http://localhost:${embedPort}`,
 				prefix: '/embed_vite',
 				rewritePrefix: '/embed_vite',
 			});
diff --git a/packages/frontend-embed/vite.config.ts b/packages/frontend-embed/vite.config.ts
index 13f272612c..1cd47b2754 100644
--- a/packages/frontend-embed/vite.config.ts
+++ b/packages/frontend-embed/vite.config.ts
@@ -2,8 +2,6 @@ import path from 'path';
 import pluginVue from '@vitejs/plugin-vue';
 import { type UserConfig, defineConfig } from 'vite';
 import { localesVersion } from '../../locales/version.js';
-import * as yaml from 'js-yaml';
-import { promises as fsp } from 'fs';
 
 import locales from '../../locales/index.js';
 import meta from '../../package.json';
@@ -11,9 +9,6 @@ import packageInfo from './package.json' with { type: 'json' };
 import pluginJson5 from './vite.json5.js';
 import { pluginReplaceIcons } from '../frontend/vite.replaceIcons.js';
 
-const url = process.env.NODE_ENV === 'development' ? yaml.load(await fsp.readFile('../../.config/default.yml', 'utf-8')).url : null;
-const host = url ? (new URL(url)).hostname : undefined;
-
 const extensions = ['.ts', '.tsx', '.js', '.jsx', '.mjs', '.json', '.json5', '.svg', '.sass', '.scss', '.css', '.vue'];
 
 /**
@@ -69,7 +64,6 @@ export function getConfig(): UserConfig {
 		base: '/embed_vite/',
 
 		server: {
-			host,
 			port: 5174,
 			hmr: {
 				// バックエンド経由での起動時、Viteは5174経由でアセットを参照していると思い込んでいるが実際は3000から配信される
diff --git a/packages/frontend/vite.config.ts b/packages/frontend/vite.config.ts
index 51940486bd..5ff07d05c9 100644
--- a/packages/frontend/vite.config.ts
+++ b/packages/frontend/vite.config.ts
@@ -3,8 +3,6 @@ import pluginReplace from '@rollup/plugin-replace';
 import pluginVue from '@vitejs/plugin-vue';
 import { type UserConfig, defineConfig } from 'vite';
 import { localesVersion } from '../../locales/version.js';
-import * as yaml from 'js-yaml';
-import { promises as fsp } from 'fs';
 
 import locales from '../../locales/index.js';
 import meta from '../../package.json';
@@ -13,9 +11,6 @@ import pluginUnwindCssModuleClassName from './lib/rollup-plugin-unwind-css-modul
 import pluginJson5 from './vite.json5.js';
 import { pluginReplaceIcons } from './vite.replaceIcons.js';
 
-const url = process.env.NODE_ENV === 'development' ? yaml.load(await fsp.readFile('../../.config/default.yml', 'utf-8')).url : null;
-const host = url ? (new URL(url)).hostname : undefined;
-
 const extensions = ['.ts', '.tsx', '.js', '.jsx', '.mjs', '.json', '.json5', '.svg', '.sass', '.scss', '.css', '.vue', '.wasm'];
 
 /**
@@ -82,7 +77,6 @@ export function getConfig(): UserConfig {
 		base: '/vite/',
 
 		server: {
-			host,
 			port: 5173,
 			hmr: {
 				// バックエンド経由での起動時、Viteは5173経由でアセットを参照していると思い込んでいるが実際は3000から配信される