diff --git a/package.json b/package.json
index 907b6fcb65..212d51cf2b 100644
--- a/package.json
+++ b/package.json
@@ -27,9 +27,9 @@
 		"build": "pnpm build-pre && pnpm -r build && pnpm build-assets",
 		"build-storybook": "pnpm --filter frontend build-storybook",
 		"build-misskey-js-with-types": "pnpm build-pre && pnpm --filter backend... --filter=!misskey-js build && pnpm --filter backend generate-api-json --no-build && ncp packages/backend/built/api.json packages/misskey-js/generator/api.json && pnpm --filter misskey-js update-autogen-code && pnpm --filter misskey-js build && pnpm --filter misskey-js api",
-		"start": "pnpm check:connect && cd packages/backend && node ./built/boot/entry.js",
-		"start:inspect": "cd packages/backend && node --inspect ./built/boot/entry.js",
-		"start:test": "ncp ./.github/misskey/test.yml ./.config/test.yml && cd packages/backend && cross-env NODE_ENV=test node ./built/boot/entry.js",
+		"start": "pnpm check:connect && cd packages/backend && pnpm convert:config && node ./built/boot/entry.js",
+		"start:inspect": "cd packages/backend && pnpm convert:config && node --inspect ./built/boot/entry.js",
+		"start:test": "ncp ./.github/misskey/test.yml ./.config/test.yml && cd packages/backend && pnpm convert:config && cross-env NODE_ENV=test node ./built/boot/entry.js",
 		"cli": "cd packages/backend && pnpm cli",
 		"init": "pnpm migrate",
 		"migrate": "cd packages/backend && pnpm migrate",
diff --git a/packages/backend/package.json b/packages/backend/package.json
index dad664d0ca..25d84a1e14 100644
--- a/packages/backend/package.json
+++ b/packages/backend/package.json
@@ -7,36 +7,37 @@
 		"node": "^22.15.0 || ^24.10.0"
 	},
 	"scripts": {
-		"start": "node ./built/boot/entry.js",
-		"start:inspect": "node --inspect ./built/boot/entry.js",
-		"start:test": "cross-env NODE_ENV=test node ./built/boot/entry.js",
-		"migrate": "pnpm typeorm migration:run -d ormconfig.js",
-		"revert": "pnpm typeorm migration:revert -d ormconfig.js",
-		"cli": "node ./built/boot/cli.js",
-		"check:connect": "node ./scripts/check_connect.js",
+		"start": "pnpm convert:config && node ./built/boot/entry.js",
+		"start:inspect": "pnpm convert:config && node --inspect ./built/boot/entry.js",
+		"start:test": "pnpm convert:config && cross-env NODE_ENV=test node ./built/boot/entry.js",
+		"migrate": "pnpm convert:config && pnpm typeorm migration:run -d ormconfig.js",
+		"revert": "pnpm convert:config && pnpm typeorm migration:revert -d ormconfig.js",
+		"cli": "pnpm convert:config && node ./built/boot/cli.js",
+		"check:connect": "pnpm convert:config && node ./scripts/check_connect.js",
+		"convert:config": "node ./scripts/convert_config.js",
 		"build": "swc src -d built -D --strip-leading-paths",
 		"build:test": "swc test-server -d built-test -D --config-file test-server/.swcrc --strip-leading-paths",
 		"watch:swc": "swc src -d built -D -w --strip-leading-paths",
 		"build:tsc": "tsc -p tsconfig.json && tsc-alias -p tsconfig.json",
-		"watch": "node ./scripts/watch.mjs",
+		"watch": "pnpm convert:config && node ./scripts/watch.mjs",
 		"restart": "pnpm build && pnpm start",
-		"dev": "node ./scripts/dev.mjs",
+		"dev": "pnpm convert:config && node ./scripts/dev.mjs",
 		"typecheck": "tsc --noEmit && tsc -p test --noEmit && tsc -p test-federation --noEmit",
 		"eslint": "eslint --quiet \"{src,test-federation}/**/*.ts\"",
 		"lint": "pnpm typecheck && pnpm eslint",
-		"jest": "cross-env NODE_ENV=test node ./jest.js --forceExit --config jest.config.unit.cjs",
-		"jest:e2e": "cross-env NODE_ENV=test node ./jest.js --forceExit --config jest.config.e2e.cjs",
-		"jest:fed": "node ./jest.js --forceExit --config jest.config.fed.cjs",
-		"jest-and-coverage": "cross-env NODE_ENV=test node ./jest.js --coverage --forceExit --config jest.config.unit.cjs",
-		"jest-and-coverage:e2e": "cross-env NODE_ENV=test node ./jest.js --coverage --forceExit --config jest.config.e2e.cjs",
-		"jest-clear": "cross-env NODE_ENV=test node ./jest.js --clearCache",
+		"jest": "pnpm convert:config && cross-env NODE_ENV=test node ./jest.js --forceExit --config jest.config.unit.cjs",
+		"jest:e2e": "pnpm convert:config && cross-env NODE_ENV=test node ./jest.js --forceExit --config jest.config.e2e.cjs",
+		"jest:fed": "pnpm convert:config && node ./jest.js --forceExit --config jest.config.fed.cjs",
+		"jest-and-coverage": "pnpm convert:config && cross-env NODE_ENV=test node ./jest.js --coverage --forceExit --config jest.config.unit.cjs",
+		"jest-and-coverage:e2e": "pnpm convert:config && cross-env NODE_ENV=test node ./jest.js --coverage --forceExit --config jest.config.e2e.cjs",
+		"jest-clear": "pnpm convert:config && cross-env NODE_ENV=test node ./jest.js --clearCache",
 		"test": "pnpm jest",
 		"test:e2e": "pnpm build && pnpm build:test && pnpm jest:e2e",
 		"test:fed": "pnpm jest:fed",
 		"test-and-coverage": "pnpm jest-and-coverage",
 		"test-and-coverage:e2e": "pnpm build && pnpm build:test && pnpm jest-and-coverage:e2e",
 		"check-migrations": "node scripts/check_migrations_clean.js",
-		"generate-api-json": "node ./scripts/generate_api_json.js"
+		"generate-api-json": "pnpm convert:config && node ./scripts/generate_api_json.js"
 	},
 	"optionalDependencies": {
 		"@swc/core-android-arm64": "1.3.11",
@@ -128,7 +129,6 @@
 		"ip-cidr": "4.0.2",
 		"ipaddr.js": "2.2.0",
 		"is-svg": "6.1.0",
-		"js-yaml": "4.1.1",
 		"json5": "2.2.3",
 		"jsonld": "9.0.0",
 		"jsrsasign": "11.1.0",
@@ -198,7 +198,6 @@
 		"@types/fluent-ffmpeg": "2.1.28",
 		"@types/http-link-header": "1.0.7",
 		"@types/jest": "29.5.14",
-		"@types/js-yaml": "4.0.9",
 		"@types/jsonld": "1.5.15",
 		"@types/jsrsasign": "10.5.15",
 		"@types/mime-types": "3.0.1",
@@ -233,6 +232,7 @@
 		"jest": "29.7.0",
 		"jest-mock": "29.7.0",
 		"jest-util": "29.7.0",
+		"js-yaml": "4.1.1",
 		"nodemon": "3.1.11",
 		"pid-port": "2.0.0",
 		"simple-oauth2": "5.1.0",
diff --git a/packages/backend/scripts/convert_config.js b/packages/backend/scripts/convert_config.js
new file mode 100644
index 0000000000..32576621cb
--- /dev/null
+++ b/packages/backend/scripts/convert_config.js
@@ -0,0 +1,56 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+/**
+ * YAMLファイルをJSONファイルに変換するスクリプト
+ * ビルド前に実行し、ランタイムにjs-yamlを含まないようにする
+ */
+
+import fs from 'node:fs';
+import { resolve, dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import yaml from 'js-yaml';
+
+const _filename = fileURLToPath(import.meta.url);
+const _dirname = dirname(_filename);
+
+const configDir = resolve(_dirname, '../../../.config');
+
+/**
+ * YAMLファイルをJSONファイルに変換
+ * @param {string} ymlPath - YAMLファイルのパス
+ * @param {string} jsonPath - JSONファイルの出力パス
+ */
+function convertYamlToJson(ymlPath, jsonPath) {
+	if (!fs.existsSync(ymlPath)) {
+		console.log(`${ymlPath} が見つからないためスキップします`);
+		return;
+	}
+
+	const yamlContent = fs.readFileSync(ymlPath, 'utf-8');
+	const jsonContent = yaml.load(yamlContent);
+	fs.writeFileSync(jsonPath, JSON.stringify(jsonContent, null, 2), 'utf-8');
+	console.log(`✓ ${ymlPath} → ${jsonPath}`);
+}
+
+// default.yml と test.yml を変換
+convertYamlToJson(
+	resolve(configDir, 'default.yml'),
+	resolve(configDir, 'default.json'),
+);
+
+convertYamlToJson(
+	resolve(configDir, 'test.yml'),
+	resolve(configDir, 'test.json'),
+);
+
+// MISSKEY_CONFIG_YML 環境変数が指定されている場合も変換
+if (process.env.MISSKEY_CONFIG_YML) {
+	const customYmlPath = resolve(configDir, process.env.MISSKEY_CONFIG_YML);
+	const customJsonPath = customYmlPath.replace(/\.ya?ml$/i, '.json');
+	convertYamlToJson(customYmlPath, customJsonPath);
+}
+
+console.log('設定ファイルの変換が完了しました');
diff --git a/packages/backend/src/config.ts b/packages/backend/src/config.ts
index fc83899eb7..53946a0bdc 100644
--- a/packages/backend/src/config.ts
+++ b/packages/backend/src/config.ts
@@ -6,7 +6,6 @@
 import * as fs from 'node:fs';
 import { fileURLToPath } from 'node:url';
 import { dirname, resolve } from 'node:path';
-import * as yaml from 'js-yaml';
 import { type FastifyServerOptions } from 'fastify';
 import type * as Sentry from '@sentry/node';
 import type * as SentryVue from '@sentry/vue';
@@ -227,10 +226,10 @@ const dir = `${_dirname}/../../../.config`;
  * Path of configuration file
  */
 export const path = process.env.MISSKEY_CONFIG_YML
-	? resolve(dir, process.env.MISSKEY_CONFIG_YML)
+	? resolve(dir, process.env.MISSKEY_CONFIG_YML).replace(/\.ya?ml$/i, '.json')
 	: process.env.NODE_ENV === 'test'
-		? resolve(dir, 'test.yml')
-		: resolve(dir, 'default.yml');
+		? resolve(dir, 'test.json')
+		: resolve(dir, 'default.json');
 
 export function loadConfig(): Config {
 	const meta = JSON.parse(fs.readFileSync(`${_dirname}/../../../built/meta.json`, 'utf-8'));
@@ -244,7 +243,7 @@ export function loadConfig(): Config {
 		JSON.parse(fs.readFileSync(`${_dirname}/../../../built/_frontend_embed_vite_/manifest.json`, 'utf-8'))
 		: { 'src/boot.ts': { file: null } };
 
-	const config = yaml.load(fs.readFileSync(path, 'utf-8')) as Source;
+	const config = JSON.parse(fs.readFileSync(path, 'utf-8')) as Source;
 
 	const url = tryCreateUrl(config.url ?? process.env.MISSKEY_URL ?? '');
 	const version = meta.version;
diff --git a/packages/backend/test-federation/compose.a.yml b/packages/backend/test-federation/compose.a.yml
index 6a305b404c..1d3d8fd404 100644
--- a/packages/backend/test-federation/compose.a.yml
+++ b/packages/backend/test-federation/compose.a.yml
@@ -40,6 +40,10 @@ services:
         source: ./.config/a.test.default.yml
         target: /misskey/.config/default.yml
         read_only: true
+      - type: bind
+        source: ../scripts/convert_config.js
+        target: /misskey/packages/backend/scripts/convert_config.js
+        read_only: true
 
   db.a.test:
     extends:
diff --git a/packages/backend/test-federation/compose.b.yml b/packages/backend/test-federation/compose.b.yml
index 1158b53bae..9a3bfb8abe 100644
--- a/packages/backend/test-federation/compose.b.yml
+++ b/packages/backend/test-federation/compose.b.yml
@@ -40,6 +40,10 @@ services:
         source: ./.config/b.test.default.yml
         target: /misskey/.config/default.yml
         read_only: true
+      - type: bind
+        source: ../scripts/convert_config.js
+        target: /misskey/packages/backend/scripts/convert_config.js
+        read_only: true
 
   db.b.test:
     extends:
diff --git a/packages/backend/test-federation/compose.tpl.yml b/packages/backend/test-federation/compose.tpl.yml
index 97068171d3..ad9e127b3a 100644
--- a/packages/backend/test-federation/compose.tpl.yml
+++ b/packages/backend/test-federation/compose.tpl.yml
@@ -42,6 +42,10 @@ services:
         source: ../package.json
         target: /misskey/packages/backend/package.json
         read_only: true
+      - type: bind
+        source: ../scripts/convert_config.js
+        target: /misskey/packages/backend/scripts/convert_config.js
+        read_only: true
       - type: bind
         source: ../../misskey-js/built
         target: /misskey/packages/misskey-js/built
diff --git a/packages/backend/test-federation/compose.yml b/packages/backend/test-federation/compose.yml
index e9ac63e4f4..07c0e03f99 100644
--- a/packages/backend/test-federation/compose.yml
+++ b/packages/backend/test-federation/compose.yml
@@ -54,6 +54,10 @@ services:
         source: ../jest.js
         target: /misskey/packages/backend/jest.js
         read_only: true
+      - type: bind
+        source: ../scripts/convert_config.js
+        target: /misskey/packages/backend/scripts/convert_config.js
+        read_only: true
       - type: bind
         source: ../../misskey-js/built
         target: /misskey/packages/misskey-js/built
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 28795dfa43..46b867469c 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -267,9 +267,6 @@ importers:
       is-svg:
         specifier: 6.1.0
         version: 6.1.0
-      js-yaml:
-        specifier: 4.1.1
-        version: 4.1.1
       json5:
         specifier: 2.2.3
         version: 2.2.3
@@ -472,9 +469,6 @@ importers:
       '@types/jest':
         specifier: 29.5.14
         version: 29.5.14
-      '@types/js-yaml':
-        specifier: 4.0.9
-        version: 4.0.9
       '@types/jsonld':
         specifier: 1.5.15
         version: 1.5.15
@@ -577,6 +571,9 @@ importers:
       jest-util:
         specifier: 29.7.0
         version: 29.7.0
+      js-yaml:
+        specifier: 4.1.1
+        version: 4.1.1
       nodemon:
         specifier: 3.1.11
         version: 3.1.11