diff --git a/src/backend/common/ConfigManager.ts b/src/backend/common/ConfigManager.ts
index e44530ad..a024d113 100644
--- a/src/backend/common/ConfigManager.ts
+++ b/src/backend/common/ConfigManager.ts
@@ -278,6 +278,7 @@ const migrations: [string, (store: Record<string, unknown>) => unknown][] = [
   [
     ">=1.1",
     (config) => {
+
       // プリセット機能を実験的機能から通常機能に
       const experimentalSetting =
         config.experimentalSetting as ExperimentalSettingType;
@@ -307,7 +308,10 @@ const migrations: [string, (store: Record<string, unknown>) => unknown][] = [
       const presets = config.presets as ConfigType["presets"];
       for (const preset of Object.values(presets.items)) {
         if (preset == undefined) throw new Error("preset == undefined");
-        preset.pauseLengthScale = 1;
+        if (!("pauseLengthScale" in preset)) {
+          // @ts-expect-error 存在しない場合のみ追加する
+          preset.pauseLengthScale = 1;
+        }
       }
 
       return config;
@@ -353,7 +357,7 @@ export abstract class BaseConfigManager {
       const data = await this.load();
       const version = data.__internal__.migrations.version;
       for (const [versionRange, migration] of migrations) {
-        if (!semver.satisfies(version, versionRange)) {
+        if (!semver.satisfies(version, versionRange) || version === '999.999.999') {
           log.info(`Migrating ${version} to ${versionRange} ...`);
           migration(data);
           log.info(`Migrated ${version} to ${versionRange} successfully.`);
diff --git a/src/domain/project/index.ts b/src/domain/project/index.ts
index 4b5da7a3..f275975b 100644
--- a/src/domain/project/index.ts
+++ b/src/domain/project/index.ts
@@ -310,8 +310,10 @@ export const migrateProjectFileObject = async (
 
   // ----- 以下は AivisSpeech 固有のマイグレーション処理 -----
 
-  if (semver.satisfies(projectAppVersion, "<1.1.0", semverSatisfiesOptions)) {
+  // 1.1.0 未満 -> 1.1.0 以上へのマイグレーション (開発版のみ常にマイグレーションを実行する)
+  if (semver.satisfies(projectAppVersion, "<1.1.0", semverSatisfiesOptions) || projectAppVersion === '999.999.999') {
 
+    // AivisSpeech ではソング機能は封印されているが、実装上の都合で一応マイグレーションしている
     // tracks: Track[] -> tracks: Record<TrackId, Track> + trackOrder: TrackId[]
     const newTracks: Record<TrackId, unknown> = {};
     for (const track of projectData.song.tracks) {
@@ -327,7 +329,9 @@ export const migrateProjectFileObject = async (
 
     // 文内無音倍率の追加
     for (const audioItemsKey in projectData.talk.audioItems) {
-      projectData.talk.audioItems[audioItemsKey].query.pauseLengthScale = 1;
+      if (!("pauseLengthScale" in projectData.talk.audioItems[audioItemsKey].query)) {
+        projectData.talk.audioItems[audioItemsKey].query.pauseLengthScale = 1;
+      }
     }
   }
 
diff --git a/src/store/project.ts b/src/store/project.ts
index 32d70bee..9de8b7ae 100755
--- a/src/store/project.ts
+++ b/src/store/project.ts
@@ -6,7 +6,6 @@ import {
   ProjectStoreState,
   ProjectStoreTypes,
 } from "@/store/type";
-import { TrackId } from "@/type/preload";
 import path from "@/helpers/path";
 import { getValueOrThrow, ResultError } from "@/type/result";
 import { LatestProjectType } from "@/domain/project/schema";
@@ -14,19 +13,12 @@ import {
   migrateProjectFileObject,
   ProjectFileFormatError,
 } from "@/domain/project";
-import {
-  createDefaultTempo,
-  createDefaultTimeSignature,
-  createDefaultTrack,
-  DEFAULT_TPQN,
-} from "@/sing/domain";
 import { EditorType } from "@/type/preload";
 import { IsEqual } from "@/type/utility";
 import {
   showAlertDialog,
   showQuestionDialog,
 } from "@/components/Dialog/Dialog";
-import { uuid4 } from "@/helpers/random";
 
 export const projectStoreState: ProjectStoreState = {
   savedLastCommandIds: { talk: null, song: null },