diff --git a/src/core/audio/AudioRecorder.ts b/src/core/audio/AudioRecorder.ts
index 8b1ebf6..f6ab141 100644
--- a/src/core/audio/AudioRecorder.ts
+++ b/src/core/audio/AudioRecorder.ts
@@ -390,10 +390,11 @@ export class AudioRecorder extends Disposable {
                 return;
             }
 
-            this.processingAnalyserNode.getFloatTimeDomainData(this.analyserDataBuffer);
+            const analyserBuffer = this.analyserDataBuffer as Float32Array<ArrayBuffer>;
+            this.processingAnalyserNode.getFloatTimeDomainData(analyserBuffer);
 
             // Copy the buffer to avoid mutation before processing completes
-            const audioData = new Float32Array(this.analyserDataBuffer);
+            const audioData = new Float32Array(analyserBuffer);
             try {
                 this.processAudioData(audioData);
             } catch (error) {
diff --git a/src/core/audio/AudioVisualizer.ts b/src/core/audio/AudioVisualizer.ts
index ccc22b1..a37e037 100644
--- a/src/core/audio/AudioVisualizer.ts
+++ b/src/core/audio/AudioVisualizer.ts
@@ -68,15 +68,16 @@ export class AudioVisualizer extends Disposable {
         this.animationId = requestAnimationFrame(() => this.draw());
 
         // Get time domain data (waveform)
-        this.analyser.getByteTimeDomainData(this.dataArray);
+        const waveformArray = this.dataArray as Uint8Array<ArrayBuffer>;
+        this.analyser.getByteTimeDomainData(waveformArray);
 
         // Calculate RMS (Root Mean Square) for current audio level
         let sum = 0;
-        for (let i = 0; i < this.dataArray.length; i++) {
-            const normalized = (this.dataArray[i] - 128) / 128;
+        for (let i = 0; i < waveformArray.length; i++) {
+            const normalized = (waveformArray[i] - 128) / 128;
             sum += normalized * normalized;
         }
-        const rms = Math.sqrt(sum / this.dataArray.length);
+        const rms = Math.sqrt(sum / waveformArray.length);
         this.currentLevel = rms;
 
         // Apply scaling factor to make waveform more visible
@@ -285,13 +286,14 @@ export class SimpleAudioLevelIndicator extends Disposable {
 
         this.animationId = requestAnimationFrame(() => this.update());
 
-        this.analyser.getByteFrequencyData(this.dataArray);
+        const frequencyArray = this.dataArray as Uint8Array<ArrayBuffer>;
+        this.analyser.getByteFrequencyData(frequencyArray);
 
         // Calculate average level with emphasis on lower frequencies (voice range)
         let sum = 0;
-        const relevantBins = Math.min(this.dataArray.length / 4, 50); // Focus on voice frequencies
+        const relevantBins = Math.min(frequencyArray.length / 4, 50); // Focus on voice frequencies
         for (let i = 0; i < relevantBins; i++) {
-            sum += this.dataArray[i];
+            sum += frequencyArray[i];
         }
         const average = sum / relevantBins;
         // Apply scaling for better visibility
diff --git a/src/plugin/VoiceInputPlugin.ts b/src/plugin/VoiceInputPlugin.ts
index b3d1dfc..f67d207 100644
--- a/src/plugin/VoiceInputPlugin.ts
+++ b/src/plugin/VoiceInputPlugin.ts
@@ -1,7 +1,7 @@
 import {
     Plugin
 } from 'obsidian';
-import { VoiceInputSettings, DEFAULT_SETTINGS } from '../interfaces';
+import { VoiceInputSettings, DEFAULT_SETTINGS, Locale, SUPPORTED_LOCALES } from '../interfaces';
 import { VoiceInputView, VIEW_TYPE_VOICE_INPUT } from '../views';
 import { VoiceInputSettingTab } from '../settings';
 import { ViewManager, DraftManager } from '../managers';
@@ -11,7 +11,12 @@ import { serviceLocator, ServiceKeys, getI18nService } from '../services';
 import { getObsidianLocale } from '../types';
 import { SafeStorageService } from '../security';
 
-type LegacyVoiceInputSettings = Partial<VoiceInputSettings> & {
+type LegacyAdvancedSettings = Partial<Omit<VoiceInputSettings['advanced'], 'transcriptionLanguage'>> & {
+    transcriptionLanguage?: string;
+};
+
+type LegacyVoiceInputSettings = Partial<Omit<VoiceInputSettings, 'advanced'>> & {
+    advanced?: LegacyAdvancedSettings;
     language?: string;
     interfaceLanguage?: string;
     recordingMode?: string;
@@ -19,6 +24,10 @@ type LegacyVoiceInputSettings = Partial<VoiceInputSettings> & {
     minSpeechDuration?: number;
 };
 
+const isSupportedLocale = (value: unknown): value is Locale => {
+    return typeof value === 'string' && (SUPPORTED_LOCALES as readonly string[]).includes(value as Locale);
+};
+
 export default class VoiceInputPlugin extends Plugin {
     settings: VoiceInputSettings;
     private viewManager: ViewManager;
@@ -244,7 +253,10 @@ export default class VoiceInputPlugin extends Plugin {
 
             // interfaceLanguageからpluginLanguageへの移行
             if ('interfaceLanguage' in data && !('pluginLanguage' in data)) {
-                migratedData.pluginLanguage = data.interfaceLanguage;
+                const interfaceLanguage = data.interfaceLanguage;
+                migratedData.pluginLanguage = isSupportedLocale(interfaceLanguage)
+                    ? interfaceLanguage
+                    : this.detectPluginLanguage();
                 delete migratedData.interfaceLanguage;
                 needsSave = true;
                 this.logger?.info('Migrating interfaceLanguage to pluginLanguage');
@@ -254,7 +266,7 @@ export default class VoiceInputPlugin extends Plugin {
             if ('language' in data && !('transcriptionLanguage' in data)) {
                 // 既存のlanguageフィールドをtranscriptionLanguageに移行
                 const langValue = data.language;
-                if (langValue === 'ja' || langValue === 'en' || langValue === 'zh' || langValue === 'ko') {
+                if (isSupportedLocale(langValue)) {
                     migratedData.transcriptionLanguage = langValue;
                 } else if (langValue === 'auto') {
                     // auto は廃止: 起動環境のロケールへ固定
@@ -270,8 +282,8 @@ export default class VoiceInputPlugin extends Plugin {
             // languageからpluginLanguageへの移行（古いバージョンとの互換性のため）
             if ('language' in data && !('pluginLanguage' in data)) {
                 // 言語コードを正規化（ja → ja、en → en、zh → zh、ko → ko、その他 → en）
-                const langCode = data.language as string;
-                if (langCode === 'ja' || langCode === 'en' || langCode === 'zh' || langCode === 'ko') {
+                const langCode = data.language;
+                if (isSupportedLocale(langCode)) {
                     migratedData.pluginLanguage = langCode;
                 } else {
                     migratedData.pluginLanguage = 'en';
@@ -306,7 +318,7 @@ export default class VoiceInputPlugin extends Plugin {
             }
 
             // 保存されたデータをデフォルト設定に上書き（undefinedの値は除外）
-            mergeSettings(this.settings, migratedData);
+            mergeSettings(this.settings, migratedData as Partial<VoiceInputSettings>);
 
             // APIキーの復号化
             if (this.settings.openaiApiKey) {
@@ -363,14 +375,13 @@ export default class VoiceInputPlugin extends Plugin {
                 };
                 needsSave = true;
                 this.logger?.info('Initialized advanced settings with language linking enabled for backward compatibility');
-            } else if (data.advanced && !hasSettingsKey(data.advanced, 'languageLinkingEnabled')) {
-                // advancedオブジェクトは存在するが、languageLinkingEnabledが無い場合
-                this.settings.advanced.languageLinkingEnabled = true;
-                needsSave = true;
-                this.logger?.info('Added languageLinkingEnabled to existing advanced settings');
             } else if (data.advanced) {
-                // auto からの置換
-                const adv = data.advanced as { transcriptionLanguage?: string };
+                const adv = data.advanced as LegacyAdvancedSettings;
+                if (typeof adv.languageLinkingEnabled === 'undefined') {
+                    this.settings.advanced.languageLinkingEnabled = true;
+                    needsSave = true;
+                    this.logger?.info('Added languageLinkingEnabled to existing advanced settings');
+                }
                 if (adv.transcriptionLanguage === 'auto') {
                     this.settings.advanced.transcriptionLanguage = this.detectPluginLanguage();
                     needsSave = true;
diff --git a/src/security/SafeStorageService.ts b/src/security/SafeStorageService.ts
index 981dd2e..f34d09e 100644
--- a/src/security/SafeStorageService.ts
+++ b/src/security/SafeStorageService.ts
@@ -35,11 +35,19 @@ const isElectronWindow = (win: Window): win is ElectronWindow => {
 };
 
 const resolveElectronRenderer = (): ElectronRenderer | null => {
-    if (isElectronWindow(window) && typeof (window as ElectronWindow).require === 'function') {
-        return (window as ElectronWindow).require('electron') ?? null;
+    if (isElectronWindow(window)) {
+        const electronWindow = window as ElectronWindow;
+        const requireFn = electronWindow.require;
+        if (typeof requireFn === 'function') {
+            return requireFn('electron') ?? null;
+        }
+        if (electronWindow.electron) {
+            return electronWindow.electron ?? null;
+        }
     }
-    if ((window as ElectronWindow).electron) {
-        return (window as ElectronWindow).electron ?? null;
+    const windowElectron = (window as ElectronWindow).electron;
+    if (windowElectron) {
+        return windowElectron ?? null;
     }
     return (globalThis as ElectronGlobal).electron ?? null;
 };
diff --git a/src/settings/VoiceInputSettingTab.ts b/src/settings/VoiceInputSettingTab.ts
index 07b0d91..ba51024 100644
--- a/src/settings/VoiceInputSettingTab.ts
+++ b/src/settings/VoiceInputSettingTab.ts
@@ -28,6 +28,17 @@ const isTranscriptionModel = (value: string): value is TranscriptionModelOption
 const isVadMode = (value: string): value is VadModeOption =>
     value === 'server' || value === 'local' || value === 'disabled';
 
+const toArrayBuffer = (view: Uint8Array): ArrayBuffer => {
+    const { buffer, byteOffset, byteLength } = view;
+    if (buffer instanceof ArrayBuffer) {
+        return byteOffset === 0 && byteLength === buffer.byteLength
+            ? buffer
+            : buffer.slice(byteOffset, byteOffset + byteLength);
+    }
+    const clone = Uint8Array.from(view);
+    return clone.buffer instanceof ArrayBuffer ? clone.buffer : new ArrayBuffer(0);
+};
+
 interface DictionaryExportData {
     version: string;
     definiteCorrections: CorrectionEntry[];
@@ -335,7 +346,7 @@ export class VoiceInputSettingTab extends PluginSettingTab {
                                 }
 
                                 const wasmTarget = getLocalVadAssetPath(this.app, wasmFileName);
-                                await adapter.writeBinary(wasmTarget, wasmBytes);
+                                await adapter.writeBinary(wasmTarget, toArrayBuffer(wasmBytes));
 
                                 let loaderPresent = await adapter.exists(getLocalVadAssetPath(this.app, loaderFileName));
                                 if (jsFile) {
diff --git a/src/views/VoiceInputView.ts b/src/views/VoiceInputView.ts
index c04a24c..394c16f 100644
--- a/src/views/VoiceInputView.ts
+++ b/src/views/VoiceInputView.ts
@@ -1,4 +1,5 @@
 import {
+    Events,
     ItemView,
     WorkspaceLeaf
 } from 'obsidian';
@@ -41,10 +42,12 @@ export class VoiceInputView extends ItemView {
         return 'microphone';
     }
 
-    onOpen(): void {
-        void this.handleOpen().catch((error) => {
+    async onOpen(): Promise<void> {
+        try {
+            await this.handleOpen();
+        } catch (error) {
             console.error('Failed to open Voice Input view', error);
-        });
+        }
     }
 
     private async handleOpen(): Promise<void> {
@@ -75,7 +78,8 @@ export class VoiceInputView extends ItemView {
             this.setupPeriodicSave();
 
             // Subscribe to settings change events to keep UI toggles in sync
-            const eventRef = this.app.workspace.on('voice-input:settings-changed', () => {
+            const workspaceEvents = this.app.workspace as Events;
+            const eventRef = workspaceEvents.on('voice-input:settings-changed', () => {
                 this.ui?.updateSettingsUI();
                 this.actions?.updateTranscriptionService();
             });
@@ -84,10 +88,12 @@ export class VoiceInputView extends ItemView {
         }
     }
 
-    onClose(): void {
-        void this.handleClose().catch((error) => {
+    async onClose(): Promise<void> {
+        try {
+            await this.handleClose();
+        } catch (error) {
             console.error('Failed to close Voice Input view', error);
-        });
+        }
     }
 
     private async handleClose(): Promise<void> {
diff --git a/tsconfig.json b/tsconfig.json
index 0dd8329..f6640d8 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -4,14 +4,14 @@
     "inlineSourceMap": true,
     "inlineSources": true,
     "module": "ESNext",
-    "target": "ES6",
+    "target": "ES2018",
     "allowJs": true,
     "noImplicitAny": true,
     "moduleResolution": "node",
     "importHelpers": true,
     "isolatedModules": true,
     "strictNullChecks": true,
-    "lib": ["DOM", "ES5", "ES6", "ES7", "ES2015.Iterable", "DOM.Iterable"]
+    "lib": ["DOM", "ES2018", "DOM.Iterable"]
   },
   "include": ["**/*.ts", "src/types/**/*.d.ts"],
   "exclude": [
@@ -20,4 +20,4 @@
     "build/**",
     "tests/**"
   ]
-}
\ No newline at end of file
+}