fix(editor): Fix i18n package locale files hot reloading (no-changelog) (#19385)

Co-authored-by: Csaba Tuncsik <csaba.tuncsik@gmail.com>

packages/frontend/@n8n/i18n/src/index.test.ts

@@ -1,6 +1,32 @@
-import { I18nClass } from './index';
+/* eslint-disable id-denylist */
+import { I18nClass, loadLanguage, i18nInstance } from './index';
+
+// Store original state for cleanup
+let originalLocale: string;
+let originalHtmlLang: string;
+const testLocales = new Set<string>();
 
 describe(I18nClass, () => {
+	beforeAll(() => {
+		// Set up basic i18n messages for displayTimer tests
+		i18nInstance.global.setLocaleMessage('en', {
+			genericHelpers: {
+				millis: 'ms',
+				secShort: 's',
+				minShort: 'm',
+				hrsShort: 'h',
+			},
+		});
+		originalLocale = i18nInstance.global.locale.value;
+		originalHtmlLang = document.querySelector('html')?.getAttribute('lang') ?? 'en';
+	});
+
+	afterAll(() => {
+		// Restore original locale and html lang
+		i18nInstance.global.locale.value = originalLocale as 'en';
+		document.querySelector('html')?.setAttribute('lang', originalHtmlLang);
+	});
+
 	describe('displayTimer', () => {
 		it('should format duration with hours, minutes and seconds', () => {
 			expect(new I18nClass().displayTimer(-1)).toBe('-1s');
@@ -33,3 +59,325 @@ describe(I18nClass, () => {
 		});
 	});
 });
+
+describe('loadLanguage', () => {
+	beforeEach(() => {
+		// Reset to English before each test
+		i18nInstance.global.locale.value = 'en';
+		document.querySelector('html')?.setAttribute('lang', 'en');
+	});
+
+	afterEach(() => {
+		// Clean up test locales (we can't easily remove them, but we can reset to English)
+		i18nInstance.global.locale.value = 'en';
+		document.querySelector('html')?.setAttribute('lang', 'en');
+	});
+
+	it('should load a new language and set it as current locale', () => {
+		const locale = 'de';
+		const messages = {
+			hello: 'Hallo',
+			world: 'Welt',
+		};
+
+		const result = loadLanguage(locale, messages);
+
+		expect(result).toBe(locale);
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		expect(i18nInstance.global.t('hello')).toBe('Hallo');
+		expect(i18nInstance.global.t('world')).toBe('Welt');
+		testLocales.add(locale);
+	});
+
+	it('should set the HTML lang attribute when loading a language', () => {
+		const locale = 'fr';
+		const messages = { greeting: 'Bonjour' };
+
+		loadLanguage(locale, messages);
+
+		expect(document.querySelector('html')?.getAttribute('lang')).toBe(locale);
+		testLocales.add(locale);
+	});
+
+	it('should handle number formats when provided in messages', () => {
+		const locale = 'de-num';
+		const messages = {
+			hello: 'Hallo',
+			numberFormats: {
+				currency: {
+					style: 'currency',
+					currency: 'EUR',
+				},
+			},
+		};
+
+		loadLanguage(locale, messages);
+
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		expect(i18nInstance.global.t('hello')).toBe('Hallo');
+		// Verify that numberFormats were set
+		expect(i18nInstance.global.getNumberFormat(locale)).toBeDefined();
+		testLocales.add(locale);
+	});
+
+	it('should not reload a language if it has already been loaded', () => {
+		const locale = 'es';
+		const originalMessages = { hello: 'Hola' };
+		const newMessages = { hello: 'Buenos días' };
+
+		// Load the language for the first time
+		loadLanguage(locale, originalMessages);
+		expect(i18nInstance.global.t('hello')).toBe('Hola');
+
+		// Switch to English temporarily
+		i18nInstance.global.locale.value = 'en';
+
+		// Try to load the same language again with different messages
+		const result = loadLanguage(locale, newMessages);
+
+		// Should return the locale but not update the messages
+		expect(result).toBe(locale);
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		expect(i18nInstance.global.t('hello')).toBe('Hola'); // Should still be the original message
+		testLocales.add(locale);
+	});
+
+	it('should handle empty messages object', () => {
+		const locale = 'it';
+		const messages = {};
+
+		const result = loadLanguage(locale, messages);
+
+		expect(result).toBe(locale);
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		testLocales.add(locale);
+	});
+
+	it('should handle messages with nested objects', () => {
+		const locale = 'pt';
+		const messages = {
+			nested: {
+				deep: {
+					message: 'Mensagem aninhada',
+				},
+			},
+			simple: 'Simples',
+		};
+
+		loadLanguage(locale, messages);
+
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		expect(i18nInstance.global.t('nested.deep.message')).toBe('Mensagem aninhada');
+		expect(i18nInstance.global.t('simple')).toBe('Simples');
+		testLocales.add(locale);
+	});
+
+	it('should properly separate numberFormats from other messages', () => {
+		const locale = 'ja';
+		const messages = {
+			greeting: 'こんにちは',
+			farewell: 'さようなら',
+			numberFormats: {
+				currency: {
+					style: 'currency',
+					currency: 'JPY',
+				},
+				decimal: {
+					style: 'decimal',
+					minimumFractionDigits: 2,
+				},
+			},
+		};
+
+		loadLanguage(locale, messages);
+
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		expect(i18nInstance.global.t('greeting')).toBe('こんにちは');
+		expect(i18nInstance.global.t('farewell')).toBe('さようなら');
+		// numberFormats should not be accessible as regular translation messages
+		expect(i18nInstance.global.te('numberFormats')).toBe(false);
+		expect(i18nInstance.global.te('numberFormats.currency')).toBe(false);
+		testLocales.add(locale);
+	});
+
+	it('should switch between already loaded languages', () => {
+		const locale1 = 'fr-switch';
+		const locale2 = 'de-switch';
+
+		// Load first language
+		loadLanguage(locale1, { hello: 'Bonjour' });
+		expect(i18nInstance.global.locale.value).toBe(locale1);
+		expect(i18nInstance.global.t('hello')).toBe('Bonjour');
+
+		// Load second language
+		loadLanguage(locale2, { hello: 'Hallo' });
+		expect(i18nInstance.global.locale.value).toBe(locale2);
+		expect(i18nInstance.global.t('hello')).toBe('Hallo');
+
+		// Switch back to first language (should not reload messages)
+		loadLanguage(locale1, { hello: 'Salut' }); // Different message
+		expect(i18nInstance.global.locale.value).toBe(locale1);
+		expect(i18nInstance.global.t('hello')).toBe('Bonjour'); // Should be original message
+		testLocales.add(locale1);
+		testLocales.add(locale2);
+	});
+
+	it('should return the locale that was set', () => {
+		const locale = 'nl';
+		const messages = { test: 'test' };
+
+		const result = loadLanguage(locale, messages);
+
+		expect(result).toBe(locale);
+		expect(typeof result).toBe('string');
+		testLocales.add(locale);
+	});
+
+	it('should handle messages with special characters', () => {
+		const locale = 'zh';
+		const messages = {
+			special: '特殊字符测试',
+			emoji: '🚀 测试 🎉',
+			mixed: 'Mixed 混合 content',
+		};
+
+		loadLanguage(locale, messages);
+
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		expect(i18nInstance.global.t('special')).toBe('特殊字符测试');
+		expect(i18nInstance.global.t('emoji')).toBe('🚀 测试 🎉');
+		expect(i18nInstance.global.t('mixed')).toBe('Mixed 混合 content');
+		testLocales.add(locale);
+	});
+
+	it('should handle messages with undefined and null values', () => {
+		const locale = 'test-null';
+		const messages = {
+			defined: 'Valid message',
+			undefined,
+			null: null,
+		};
+
+		loadLanguage(locale, messages);
+
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		expect(i18nInstance.global.t('defined')).toBe('Valid message');
+		// Undefined and null values should fallback to the key
+		expect(i18nInstance.global.t('undefined')).toBe('undefined');
+		expect(i18nInstance.global.t('null')).toBe('null');
+		testLocales.add(locale);
+	});
+
+	it('should handle messages with array values', () => {
+		const locale = 'test-array';
+		const messages = {
+			items: ['item1', 'item2', 'item3'],
+			nested: {
+				list: ['a', 'b', 'c'],
+			},
+		};
+
+		loadLanguage(locale, messages);
+
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		// Vue i18n handles arrays, but accessing them directly might not work as expected
+		// This tests that the function doesn't crash with array values
+		expect(() => i18nInstance.global.t('items')).not.toThrow();
+		testLocales.add(locale);
+	});
+
+	it('should handle loading the same locale as current locale', () => {
+		const currentLocale = 'en';
+		const messages = {
+			newMessage: 'This is a new message',
+		};
+
+		// Ensure we're starting with English
+		i18nInstance.global.locale.value = currentLocale;
+
+		const result = loadLanguage(currentLocale, messages);
+
+		expect(result).toBe(currentLocale);
+		expect(i18nInstance.global.locale.value).toBe(currentLocale);
+		expect(i18nInstance.global.t('newMessage')).toBe('This is a new message');
+	});
+
+	it('should handle numberFormats with complex structure', () => {
+		const locale = 'complex-number';
+		const messages = {
+			greeting: 'Hello',
+			numberFormats: {
+				currency: {
+					style: 'currency',
+					currency: 'USD',
+					currencyDisplay: 'symbol',
+				},
+				percent: {
+					style: 'percent',
+					minimumFractionDigits: 2,
+				},
+				decimal: {
+					style: 'decimal',
+					minimumFractionDigits: 0,
+					maximumFractionDigits: 3,
+				},
+			},
+		};
+
+		loadLanguage(locale, messages);
+
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		expect(i18nInstance.global.t('greeting')).toBe('Hello');
+
+		const numberFormats = i18nInstance.global.getNumberFormat(
+			locale,
+		) as typeof messages.numberFormats;
+		expect(numberFormats).toBeDefined();
+		expect(numberFormats.currency).toBeDefined();
+		expect(numberFormats.percent).toBeDefined();
+		expect(numberFormats.decimal).toBeDefined();
+		testLocales.add(locale);
+	});
+
+	it('should handle messages with boolean and numeric values', () => {
+		const locale = 'test-types';
+		const messages = {
+			boolTrue: true,
+			boolFalse: false,
+			number: 42,
+			zero: 0,
+			string: 'actual string',
+		};
+
+		loadLanguage(locale, messages);
+
+		expect(i18nInstance.global.locale.value).toBe(locale);
+		expect(i18nInstance.global.t('string')).toBe('actual string');
+		// Boolean and numeric values that are not strings will fallback to the key name
+		// This is the expected behavior of vue-i18n when values are not strings
+		expect(i18nInstance.global.t('boolTrue')).toBe('boolTrue');
+		expect(i18nInstance.global.t('boolFalse')).toBe('boolFalse');
+		expect(i18nInstance.global.t('number')).toBe('number');
+		expect(i18nInstance.global.t('zero')).toBe('zero');
+		testLocales.add(locale);
+	});
+
+	it('should preserve HTML document language attribute correctly', () => {
+		const html = document.querySelector('html');
+		const originalLang = html?.getAttribute('lang') ?? 'en';
+
+		const locale1 = 'preserve-1';
+		const locale2 = 'preserve-2';
+
+		loadLanguage(locale1, { test: 'test1' });
+		expect(html?.getAttribute('lang')).toBe(locale1);
+
+		loadLanguage(locale2, { test: 'test2' });
+		expect(html?.getAttribute('lang')).toBe(locale2);
+
+		// Restore original
+		html?.setAttribute('lang', originalLang);
+		testLocales.add(locale1);
+		testLocales.add(locale2);
+	});
+});

packages/frontend/@n8n/i18n/src/index.ts

@@ -1,8 +1,8 @@
 /* eslint-disable @typescript-eslint/no-this-alias */
 import type { INodeProperties, INodePropertyCollection, INodePropertyOptions } from 'n8n-workflow';
+import { ref } from 'vue';
 import { createI18n } from 'vue-i18n';
 
-import englishBaseText from './locales/en.json';
 import type { BaseTextKey, INodeTranslationHeaders } from './types';
 import {
 	deriveMiddleKey,
@@ -17,10 +17,13 @@ export const i18nInstance = createI18n({
 	legacy: false,
 	locale: 'en',
 	fallbackLocale: 'en',
-	messages: { en: englishBaseText },
+	messages: { en: {} },
 	warnHtmlMessage: false,
 });
 
+// Reactive version to signal i18n message updates to Vue computations
+export const i18nVersion = ref(0);
+
 type BaseTextOptions = {
 	adjustToNumber?: number;
 	interpolate?: Record<string, string | number>;
@@ -57,8 +60,12 @@ export class I18nClass {
 	 * Render a string of base text, i.e. a string with a fixed path to the localized value. Optionally allows for [interpolation](https://kazupon.github.io/vue-i18n/guide/formatting.html#named-formatting) when the localized value contains a string between curly braces.
 	 */
 	baseText(key: BaseTextKey, options?: BaseTextOptions): string {
-		// Create a unique cache key
+		// Track reactive version so computed properties re-evaluate when messages change
-		const cacheKey = `${key}-${JSON.stringify(options)}`;
+		// eslint-disable-next-line @typescript-eslint/no-unused-expressions
+		i18nVersion.value;
+
+		// Create a unique cache key, scoped by version
+		const cacheKey = `${i18nVersion.value}|${key}-${JSON.stringify(options)}`;
 
 		// Check if the result is already cached
 		if (this.baseTextCache.has(cacheKey)) {
@@ -79,6 +86,14 @@ export class I18nClass {
 		return result;
 	}
 
+	/**
+	 * Clear cached baseText results. Useful when locale messages are updated at runtime (e.g. HMR) or locale changes.
+	 */
+	clearCache() {
+		this.baseTextCache.clear();
+		i18nVersion.value++;
+	}
+
 	/**
 	 * Render a string of dynamic text, i.e. a string with a constructed path to the localized value.
 	 */
@@ -375,35 +390,34 @@ export class I18nClass {
 	};
 }
 
-const loadedLanguages = ['en'];
+const loadedLanguages: string[] = [];
 
-async function setLanguage(language: string) {
+export function setLanguage(locale: string) {
-	i18nInstance.global.locale.value = language as 'en';
+	i18nInstance.global.locale.value = locale as 'en';
-	document.querySelector('html')!.setAttribute('lang', language);
+	document.querySelector('html')!.setAttribute('lang', locale);
 
-	return language;
+	// Invalidate cached baseText results on locale change
+	i18n.clearCache();
+
+	return locale;
 }
 
-export async function loadLanguage(language: string) {
+export function loadLanguage(locale: string, messages: Record<string, unknown>) {
-	if (i18nInstance.global.locale.value === language) {
+	if (loadedLanguages.includes(locale)) {
-		return await setLanguage(language);
+		return setLanguage(locale);
 	}
 
-	if (loadedLanguages.includes(language)) {
+	const { numberFormats, ...rest } = messages;
-		return await setLanguage(language);
-	}
 
-	const { numberFormats, ...rest } = (await import(`@n8n/i18n/locales/${language}.json`)).default;
+	i18nInstance.global.setLocaleMessage(locale, rest);
-
-	i18nInstance.global.setLocaleMessage(language, rest);
 
 	if (numberFormats) {
-		i18nInstance.global.setNumberFormat(language, numberFormats);
+		i18nInstance.global.setNumberFormat(locale, numberFormats);
 	}
 
-	loadedLanguages.push(language);
+	loadedLanguages.push(locale);
 
-	return await setLanguage(language);
+	return setLanguage(locale);
 }
 
 /**
@@ -422,6 +436,22 @@ export function addNodeTranslation(
 	i18nInstance.global.mergeLocaleMessage(language, newMessages);
 }
 
+/**
+ * Dev/runtime helper to replace messages for a locale without import side-effects.
+ * Used by editor UI HMR to apply updated translation JSON.
+ */
+export function updateLocaleMessages(locale: string, messages: Record<string, unknown>) {
+	const { numberFormats, ...rest } = messages as Record<string, unknown> & {
+		numberFormats?: Record<string, unknown>;
+	};
+
+	i18nInstance.global.setLocaleMessage(locale, rest);
+	if (numberFormats) i18nInstance.global.setNumberFormat(locale, numberFormats);
+
+	// Ensure subsequent reads recompute
+	i18n.clearCache();
+}
+
 /**
  * Add a credential translation to the i18n instance's `messages` object.
  */

packages/frontend/@n8n/i18n/src/types.ts

@@ -3,6 +3,7 @@ import type englishBaseText from './locales/en.json';
 export type GetBaseTextKey<T> = T extends `_${string}` ? never : T;
 
 export type BaseTextKey = GetBaseTextKey<keyof typeof englishBaseText>;
+export type LocaleMessages = typeof englishBaseText;
 
 export interface INodeTranslationHeaders {
 	data: {

packages/frontend/editor-ui/src/App.vue

@@ -1,34 +1,35 @@
 <script setup lang="ts">
 import '@/polyfills';
 
-import { ref, computed, watch, onMounted, onBeforeUnmount, nextTick } from 'vue';
+import AssistantsHub from '@/components/AskAssistant/AssistantsHub.vue';
-import { useRoute } from 'vue-router';
+import AskAssistantFloatingButton from '@/components/AskAssistant/Chat/AskAssistantFloatingButton.vue';
-import LoadingView from '@/views/LoadingView.vue';
 import BannerStack from '@/components/banners/BannerStack.vue';
 import Modals from '@/components/Modals.vue';
 import Telemetry from '@/components/Telemetry.vue';
-import AskAssistantFloatingButton from '@/components/AskAssistant/Chat/AskAssistantFloatingButton.vue';
+import { useHistoryHelper } from '@/composables/useHistoryHelper';
-import AssistantsHub from '@/components/AskAssistant/AssistantsHub.vue';
+import { useTelemetryContext } from '@/composables/useTelemetryContext';
-import { loadLanguage } from '@n8n/i18n';
+import { useWorkflowDiffRouting } from '@/composables/useWorkflowDiffRouting';
 import {
 	APP_MODALS_ELEMENT_ID,
 	CODEMIRROR_TOOLTIP_CONTAINER_ELEMENT_ID,
 	HIRING_BANNER,
 	VIEWS,
 } from '@/constants';
-import { useRootStore } from '@n8n/stores/useRootStore';
 import { useAssistantStore } from '@/stores/assistant.store';
 import { useBuilderStore } from '@/stores/builder.store';
+import { useNDVStore } from '@/stores/ndv.store';
+import { useSettingsStore } from '@/stores/settings.store';
 import { useUIStore } from '@/stores/ui.store';
 import { useUsersStore } from '@/stores/users.store';
-import { useSettingsStore } from '@/stores/settings.store';
+import LoadingView from '@/views/LoadingView.vue';
-import { useHistoryHelper } from '@/composables/useHistoryHelper';
-import { useWorkflowDiffRouting } from '@/composables/useWorkflowDiffRouting';
-import { useStyles } from './composables/useStyles';
 import { locale } from '@n8n/design-system';
+import { setLanguage } from '@n8n/i18n';
+// Note: no need to import en.json here; default 'en' is handled via setLanguage
+import { useRootStore } from '@n8n/stores/useRootStore';
 import axios from 'axios';
-import { useTelemetryContext } from '@/composables/useTelemetryContext';
+import { computed, nextTick, onBeforeUnmount, onMounted, ref, watch } from 'vue';
-import { useNDVStore } from '@/stores/ndv.store';
+import { useRoute } from 'vue-router';
+import { useStyles } from './composables/useStyles';
 
 const route = useRoute();
 const rootStore = useRootStore();
@@ -100,13 +101,16 @@ watch(route, (r) => {
 
 watch(
 	defaultLocale,
-	(newLocale) => {
+	async (newLocale) => {
-		void loadLanguage(newLocale);
+		setLanguage(newLocale);
-		void locale.use(newLocale);
+
 		axios.defaults.headers.common['Accept-Language'] = newLocale;
+		void locale.use(newLocale);
 	},
 	{ immediate: true },
 );
+
+// Dev HMR for i18n is imported in main.ts before app mount
 </script>
 
 <template>

packages/frontend/editor-ui/src/__tests__/setup.ts

@@ -2,6 +2,8 @@ import '@testing-library/jest-dom';
 import 'fake-indexeddb/auto';
 import { configure } from '@testing-library/vue';
 import 'core-js/proposals/set-methods-v2';
+import englishBaseText from '@n8n/i18n/locales/en.json';
+import { loadLanguage } from '@n8n/i18n';
 import { APP_MODALS_ELEMENT_ID } from '@/constants';
 
 // Avoid tests failing because of difference between local and GitHub actions timezone
@@ -144,3 +146,5 @@ Object.defineProperty(HTMLElement.prototype, 'scrollTo', {
 	writable: true,
 	value: vi.fn(),
 });
+
+loadLanguage('en', englishBaseText);

packages/frontend/editor-ui/src/dev/i18nHmr.ts

@@ -0,0 +1,69 @@
+import { i18n, i18nInstance, setLanguage, updateLocaleMessages } from '@n8n/i18n';
+import type { LocaleMessages } from '@n8n/i18n/types';
+import { locale as designLocale } from '@n8n/design-system';
+
+const hot = import.meta.hot;
+const DEFAULT_LOCALE = 'en';
+
+if (hot) {
+	// Eagerly import locale JSONs so this module becomes their HMR owner
+	const localeModules = import.meta.glob('@n8n/i18n/locales/*.json', { eager: true }) as Record<
+		string,
+		{ default?: LocaleMessages }
+	>;
+	const localePaths = Object.keys(localeModules);
+
+	const lcOf = (p: string) => p.match(/\/locales\/([^/]+)\.json$/)?.[1] ?? DEFAULT_LOCALE;
+	const apply = (lc: string, msgs: LocaleMessages) => updateLocaleMessages(lc, msgs);
+
+	// Seed all locales on initial load in dev so switching locales
+	// does not require component-level dynamic imports (avoids hard reload chains)
+	for (const p of localePaths) {
+		const lc = lcOf(p);
+		const msgs = (localeModules[p] as { default?: LocaleMessages })?.default;
+		if (msgs && lc) apply(lc, msgs);
+	}
+	const refresh = () => {
+		const current = (i18nInstance.global.locale.value as string) || DEFAULT_LOCALE;
+		i18n.clearCache();
+		setLanguage(current);
+		void designLocale.use(current);
+	};
+	// Fetch with cache-buster to avoid stale content (one-update-behind);
+	// falls back to the eager map if network fetch is unavailable.
+	const fetchAndApply = async (file: string) => {
+		try {
+			const res = await fetch(`/@fs${file}?t=${Date.now()}`);
+			apply(lcOf(file), (await res.json()) as LocaleMessages);
+		} catch {
+			const msgs = localeModules[file]?.default;
+			if (msgs) apply(lcOf(file), msgs);
+		}
+	};
+
+	// 1) Apply fresh modules provided by Vite HMR
+	hot.accept(localePaths, (mods) => {
+		mods.forEach((mod, i) => apply(lcOf(localePaths[i] ?? DEFAULT_LOCALE), mod?.default ?? {}));
+		refresh();
+	});
+
+	// 2) Handle explicit locale update events (fetch ensures latest content)
+	hot.on('n8n:locale-update', async (payload: { locales?: string[]; file?: string }) => {
+		if (payload.file) await fetchAndApply(payload.file);
+		refresh();
+	});
+
+	// 3) Last resort for cases where accept doesn’t trigger
+	hot.on(
+		'vite:afterUpdate',
+		async (payload: { updates?: Array<{ path?: string; acceptedPath?: string }> }) => {
+			const updates = payload?.updates ?? [];
+			const files = updates
+				.map((u) => (u.path ?? u.acceptedPath ?? '') as string)
+				.filter((p) => p.includes('/locales/') && p.endsWith('.json'));
+			if (files.length === 0) return;
+			for (const file of files) await fetchAndApply(file);
+			refresh();
+		},
+	);
+}

packages/frontend/editor-ui/src/features/insights/components/InsightsDateRangeSelect.vue

@@ -3,7 +3,8 @@ import { useInsightsStore } from '@/features/insights/insights.store';
 import type { InsightsDateRange } from '@n8n/api-types';
 import { N8nOption, N8nSelect } from '@n8n/design-system';
 import { ref } from 'vue';
-import { TIME_RANGE_LABELS, UNLICENSED_TIME_RANGE } from '../insights.constants';
+import { UNLICENSED_TIME_RANGE } from '../insights.constants';
+import { getTimeRangeLabels } from '../insights.utils';
 
 const model = defineModel<InsightsDateRange['key'] | typeof UNLICENSED_TIME_RANGE>({
 	required: true,
@@ -11,11 +12,13 @@ const model = defineModel<InsightsDateRange['key'] | typeof UNLICENSED_TIME_RANG
 
 const insightsStore = useInsightsStore();
 
+const timeRangeLabels = getTimeRangeLabels();
+
 const timeOptions = ref(
 	insightsStore.dateRanges.map((option) => {
 		return {
 			key: option.key,
-			label: TIME_RANGE_LABELS[option.key],
+			label: timeRangeLabels[option.key],
 			value: option.licensed ? option.key : UNLICENSED_TIME_RANGE,
 			licensed: option.licensed,
 		};

packages/frontend/editor-ui/src/features/insights/components/InsightsSummary.vue

@@ -1,18 +1,18 @@
 <script setup lang="ts">
-import { useI18n } from '@n8n/i18n';
 import { useTelemetry } from '@/composables/useTelemetry';
 import { VIEWS } from '@/constants';
 import {
 	INSIGHT_IMPACT_TYPES,
 	INSIGHTS_UNIT_IMPACT_MAPPING,
-	TIME_RANGE_LABELS,
 } from '@/features/insights/insights.constants';
 import type { InsightsSummaryDisplay } from '@/features/insights/insights.types';
 import type { InsightsDateRange, InsightsSummary } from '@n8n/api-types';
+import { useI18n } from '@n8n/i18n';
 import { smartDecimal } from '@n8n/utils/number/smartDecimal';
 import { computed, useCssModule } from 'vue';
-import { useRoute } from 'vue-router';
 import { I18nT } from 'vue-i18n';
+import { useRoute } from 'vue-router';
+import { getTimeRangeLabels } from '../insights.utils';
 
 const props = defineProps<{
 	summary: InsightsSummaryDisplay;
@@ -25,6 +25,8 @@ const route = useRoute();
 const $style = useCssModule();
 const telemetry = useTelemetry();
 
+const timeRangeLabels = getTimeRangeLabels();
+
 const summaryTitles = computed<Record<keyof InsightsSummary, string>>(() => ({
 	total: i18n.baseText('insights.banner.title.total'),
 	failed: i18n.baseText('insights.banner.title.failed'),
@@ -94,7 +96,7 @@ const trackTabClick = (insightType: keyof InsightsSummary) => {
 							</N8nTooltip>
 						</strong>
 						<small :class="$style.days">
-							{{ TIME_RANGE_LABELS[timeRange] }}
+							{{ timeRangeLabels[timeRange] }}
 						</small>
 						<span v-if="value === 0 && id === 'timeSaved'" :class="$style.empty">
 							<em>--</em>

packages/frontend/editor-ui/src/features/insights/insights.constants.ts

@@ -1,5 +1,4 @@
 import type { InsightsSummaryType } from '@n8n/api-types';
-import { useI18n } from '@n8n/i18n';
 import dateformat from 'dateformat';
 
 export const INSIGHT_TYPES = {
@@ -79,14 +78,4 @@ export const TELEMETRY_TIME_RANGE = {
 	year: 365,
 };
 
-export const TIME_RANGE_LABELS = {
-	day: useI18n().baseText('insights.lastNHours', { interpolate: { count: 24 } }),
-	week: useI18n().baseText('insights.lastNDays', { interpolate: { count: 7 } }),
-	'2weeks': useI18n().baseText('insights.lastNDays', { interpolate: { count: 14 } }),
-	month: useI18n().baseText('insights.lastNDays', { interpolate: { count: 30 } }),
-	quarter: useI18n().baseText('insights.lastNDays', { interpolate: { count: 90 } }),
-	'6months': useI18n().baseText('insights.months', { interpolate: { count: 6 } }),
-	year: useI18n().baseText('insights.oneYear'),
-};
-
 export const UNLICENSED_TIME_RANGE = 'UNLICENSED_TIME_RANGE' as const;

packages/frontend/editor-ui/src/features/insights/insights.utils.ts

@@ -1,3 +1,4 @@
+import { useI18n } from '@n8n/i18n';
 import type { InsightsSummary, InsightsSummaryType } from '@n8n/api-types';
 import type { InsightsSummaryDisplay } from '@/features/insights/insights.types';
 import {
@@ -57,3 +58,17 @@ export const transformInsightsSummary = (data: InsightsSummary | null): Insights
 				unit: INSIGHTS_UNIT_MAPPING[key](data[key].value),
 			}))
 		: [];
+
+export const getTimeRangeLabels = () => {
+	const i18n = useI18n();
+
+	return {
+		day: i18n.baseText('insights.lastNHours', { interpolate: { count: 24 } }),
+		week: i18n.baseText('insights.lastNDays', { interpolate: { count: 7 } }),
+		'2weeks': i18n.baseText('insights.lastNDays', { interpolate: { count: 14 } }),
+		month: i18n.baseText('insights.lastNDays', { interpolate: { count: 30 } }),
+		quarter: i18n.baseText('insights.lastNDays', { interpolate: { count: 90 } }),
+		'6months': i18n.baseText('insights.months', { interpolate: { count: 6 } }),
+		year: i18n.baseText('insights.oneYear'),
+	};
+};

packages/frontend/editor-ui/src/i18n/loadDefaultEn.ts

@@ -0,0 +1,7 @@
+import { loadLanguage } from '@n8n/i18n';
+import type { LocaleMessages } from '@n8n/i18n/types';
+
+export async function loadDefaultEn() {
+	const mod = (await import('@n8n/i18n/locales/en.json')) as { default: LocaleMessages };
+	loadLanguage('en', mod.default);
+}

packages/frontend/editor-ui/src/main.ts

@@ -15,7 +15,8 @@ import './n8n-theme.scss';
 import App from '@/App.vue';
 import router from './router';
 
-import { i18nInstance } from '@n8n/i18n';
+import { i18nInstance, setLanguage } from '@n8n/i18n';
+
 import { TelemetryPlugin } from './plugins/telemetry';
 import { GlobalComponentsPlugin } from './plugins/components';
 import { GlobalDirectivesPlugin } from './plugins/directives';
@@ -34,6 +35,17 @@ const app = createApp(App);
 
 app.use(SentryPlugin);
 
+// Initialize i18n
+if (import.meta.env.DEV) {
+	// Import HMR owner early so messages are seeded before app mount
+	await import('@/dev/i18nHmr');
+	setLanguage('en');
+} else {
+	// Production: load English messages explicitly via isolated module
+	const { loadDefaultEn } = await import('@/i18n/loadDefaultEn');
+	await loadDefaultEn();
+}
+
 // Register module routes
 // We do this here so landing straight on a module page works
 registerModuleRoutes(router);

packages/frontend/editor-ui/src/shims.d.ts

@@ -1,3 +1,4 @@
+/// <reference types="vite/client" />
 /// <reference types="vite-plugin-comlink/client" />
 
 import type { VNode, ComponentPublicInstance } from 'vue';

packages/frontend/editor-ui/vite.config.mts

@@ -1,5 +1,5 @@
 import vue from '@vitejs/plugin-vue';
-import { posix as pathPosix, resolve } from 'path';
+import { posix as pathPosix, resolve, sep as pathSep } from 'path';
 import { defineConfig, mergeConfig, type UserConfig } from 'vite';
 import { viteStaticCopy } from 'vite-plugin-static-copy';
 import { nodePolyfills } from 'vite-plugin-node-polyfills';
@@ -12,6 +12,7 @@ import components from 'unplugin-vue-components/vite';
 import browserslistToEsbuild from 'browserslist-to-esbuild';
 import legacy from '@vitejs/plugin-legacy';
 import browserslist from 'browserslist';
+import { isLocaleFile, sendLocaleUpdate } from './vite/i18n-locales-hmr-helpers';
 
 const publicPath = process.env.VUE_APP_PUBLIC_PATH || '/';
 
@@ -24,6 +25,8 @@ const packagesDir = resolve(__dirname, '..', '..');
 const alias = [
 	{ find: '@', replacement: resolve(__dirname, 'src') },
 	{ find: 'stream', replacement: 'stream-browserify' },
+	// Ensure bare imports resolve to sources (not dist)
+	{ find: '@n8n/i18n', replacement: resolve(packagesDir, 'frontend', '@n8n', 'i18n', 'src') },
 	{
 		find: /^@n8n\/chat(.+)$/,
 		replacement: resolve(packagesDir, 'frontend', '@n8n', 'chat', 'src$1'),
@@ -140,6 +143,27 @@ const plugins: UserConfig['plugins'] = [
 	nodePolyfills({
 		include: ['fs', 'path', 'url', 'util', 'timers'],
 	}),
+	{
+		name: 'i18n-locales-hmr',
+		configureServer(server) {
+			const localesDir = resolve(packagesDir, 'frontend', '@n8n', 'i18n', 'src', 'locales');
+			server.watcher.add(localesDir);
+
+			// Only emit for add/unlink; change events are handled in handleHotUpdate
+			server.watcher.on('all', (event, file) => {
+				if ((event === 'add' || event === 'unlink') && isLocaleFile(file)) {
+					sendLocaleUpdate(server, file);
+				}
+			});
+		},
+		handleHotUpdate(ctx) {
+			const { file, server } = ctx;
+			if (!isLocaleFile(file)) return;
+			sendLocaleUpdate(server, file);
+			// Swallow default HMR for this file to prevent full page reloads
+			return [];
+		},
+	},
 ];
 
 const { RELEASE: release } = process.env;

packages/frontend/editor-ui/vite/i18n-locales-hmr-helpers.ts

@@ -0,0 +1,19 @@
+import { sep as pathSep } from 'path';
+
+export const isLocaleFile = (file: string): boolean =>
+	file.endsWith('.json') && file.includes(`${pathSep}locales${pathSep}`);
+
+export const extractLocale = (file: string): string | null => {
+	const match = file.match(new RegExp(`${pathSep}locales${pathSep}([^${pathSep}]+)\\.json$`));
+	return match?.[1] ?? null;
+};
+
+export const sendLocaleUpdate = (server: any, file: string): void => {
+	if (!isLocaleFile(file)) return;
+	const locale = extractLocale(file);
+	server.ws.send({
+		type: 'custom',
+		event: 'n8n:locale-update',
+		data: { locales: locale ? [locale] : [], file },
+	});
+};