feat(bot): persist locale preferences across mini app and replies

2026-03-31 13:44:03 +00:00 · 2026-03-09 13:17:46 +04:00
parent 9de6bcc31b
commit 2d8e0491cc
19 changed files with 904 additions and 77 deletions
--- a/apps/bot/src/anonymous-feedback.test.ts
+++ b/apps/bot/src/anonymous-feedback.test.ts
@@ -95,7 +95,8 @@ function createHouseholdConfigurationRepository(): HouseholdConfigurationReposit
        householdName: 'Kojori House',
        telegramChatId: '-100222333',
        telegramChatType: 'supergroup',
-        title: 'Kojori House'
+        title: 'Kojori House',
+        defaultLocale: 'ru'
      }
    }),
    getTelegramHouseholdChat: async () => ({
@@ -103,14 +104,16 @@ function createHouseholdConfigurationRepository(): HouseholdConfigurationReposit
      householdName: 'Kojori House',
      telegramChatId: '-100222333',
      telegramChatType: 'supergroup',
-      title: 'Kojori House'
+      title: 'Kojori House',
+      defaultLocale: 'ru'
    }),
    getHouseholdChatByHouseholdId: async () => ({
      householdId: 'household-1',
      householdName: 'Kojori House',
      telegramChatId: '-100222333',
      telegramChatType: 'supergroup',
-      title: 'Kojori House'
+      title: 'Kojori House',
+      defaultLocale: 'ru'
    }),
    bindHouseholdTopic: async (input) => ({
      householdId: input.householdId,
@@ -143,7 +146,8 @@ function createHouseholdConfigurationRepository(): HouseholdConfigurationReposit
      telegramUserId: input.telegramUserId,
      displayName: input.displayName,
      username: input.username?.trim() || null,
-      languageCode: input.languageCode?.trim() || null
+      languageCode: input.languageCode?.trim() || null,
+      householdDefaultLocale: 'ru'
    }),
    getPendingHouseholdMember: async () => null,
    findPendingHouseholdMemberByTelegramUserId: async () => null,
@@ -152,6 +156,8 @@ function createHouseholdConfigurationRepository(): HouseholdConfigurationReposit
      householdId: input.householdId,
      telegramUserId: input.telegramUserId,
      displayName: input.displayName,
+      preferredLocale: input.preferredLocale ?? null,
+      householdDefaultLocale: 'ru',
      isAdmin: input.isAdmin === true
    }),
    getHouseholdMember: async () => null,
@@ -162,11 +168,30 @@ function createHouseholdConfigurationRepository(): HouseholdConfigurationReposit
        householdId: 'household-1',
        telegramUserId: '123456',
        displayName: 'Stan',
+        preferredLocale: null,
+        householdDefaultLocale: 'ru',
        isAdmin: false
      }
    ],
    listPendingHouseholdMembers: async () => [],
-    approvePendingHouseholdMember: async () => null
+    approvePendingHouseholdMember: async () => null,
+    updateHouseholdDefaultLocale: async (_householdId, locale) => ({
+      householdId: 'household-1',
+      householdName: 'Kojori House',
+      telegramChatId: '-100222333',
+      telegramChatType: 'supergroup',
+      title: 'Kojori House',
+      defaultLocale: locale
+    }),
+    updateMemberPreferredLocale: async (_householdId, telegramUserId, locale) => ({
+      id: `member-${telegramUserId}`,
+      householdId: 'household-1',
+      telegramUserId,
+      displayName: 'Stan',
+      preferredLocale: locale,
+      householdDefaultLocale: 'ru',
+      isAdmin: false
+    })
  }
 }

@@ -236,10 +261,10 @@ describe('registerAnonymousFeedback', () => {
    expect(calls[0]?.payload).toMatchObject({
      chat_id: '-100222333',
      message_thread_id: 77,
-      text: 'Anonymous household note\n\nPlease clean the kitchen tonight.'
+      text: 'Анонимное сообщение по дому\n\nPlease clean the kitchen tonight.'
    })
    expect(calls[1]?.payload).toMatchObject({
-      text: 'Anonymous feedback delivered.'
+      text: 'Анонимное сообщение отправлено.'
    })
  })

@@ -303,7 +328,7 @@ describe('registerAnonymousFeedback', () => {

    expect(calls).toHaveLength(1)
    expect(calls[0]?.payload).toMatchObject({
-      text: 'Use /anon in a private chat with the bot.'
+      text: 'Используйте /anon в личном чате с ботом.'
    })
  })

@@ -377,15 +402,15 @@ describe('registerAnonymousFeedback', () => {

    expect(submit).toHaveBeenCalledTimes(1)
    expect(calls[0]?.payload).toMatchObject({
-      text: 'Send me the anonymous message in your next reply, or tap Cancel.'
+      text: 'Отправьте анонимное сообщение следующим сообщением или нажмите «Отменить».'
    })
    expect(calls[1]?.payload).toMatchObject({
      chat_id: '-100222333',
      message_thread_id: 77,
-      text: 'Anonymous household note\n\nPlease clean the kitchen tonight.'
+      text: 'Анонимное сообщение по дому\n\nPlease clean the kitchen tonight.'
    })
    expect(calls[2]?.payload).toMatchObject({
-      text: 'Anonymous feedback delivered.'
+      text: 'Анонимное сообщение отправлено.'
    })
  })

@@ -620,7 +645,7 @@ describe('registerAnonymousFeedback', () => {

    expect(calls).toHaveLength(1)
    expect(calls[0]?.payload).toMatchObject({
-      text: 'Anonymous feedback cooldown is active. You can send the next message in 6 hours.'
+      text: 'Сейчас действует пауза на анонимные сообщения. Следующее сообщение можно отправить через 6 часов.'
    })
  })
 })
--- a/apps/bot/src/anonymous-feedback.ts
+++ b/apps/bot/src/anonymous-feedback.ts
@@ -7,7 +7,8 @@ import type {
 } from '@household/ports'
 import type { Bot, Context } from 'grammy'

-import { botLocaleFromContext, getBotTranslations, type BotLocale } from './i18n'
+import { getBotTranslations, type BotLocale } from './i18n'
+import { resolveReplyLocale } from './bot-locale'

 const ANONYMOUS_FEEDBACK_ACTION = 'anonymous_feedback' as const
 const CANCEL_ANONYMOUS_FEEDBACK_CALLBACK = 'cancel_prompt:anonymous_feedback'
@@ -114,9 +115,13 @@ async function clearPendingAnonymousFeedbackPrompt(

 async function startPendingAnonymousFeedbackPrompt(
  repository: TelegramPendingActionRepository,
+  householdConfigurationRepository: HouseholdConfigurationRepository,
  ctx: Context
 ): Promise<void> {
-  const locale = botLocaleFromContext(ctx)
+  const locale = await resolveReplyLocale({
+    ctx,
+    repository: householdConfigurationRepository
+  })
  const t = getBotTranslations(locale).anonymousFeedback
  const telegramUserId = ctx.from?.id?.toString()
  const telegramChatId = ctx.chat?.id?.toString()
@@ -152,11 +157,15 @@ async function submitAnonymousFeedback(options: {
  const telegramMessageId = options.ctx.msg?.message_id?.toString()
  const telegramUpdateId =
    'update_id' in options.ctx.update ? options.ctx.update.update_id?.toString() : undefined
-  const locale = botLocaleFromContext(options.ctx)
-  const t = getBotTranslations(locale).anonymousFeedback
+  const fallbackLocale = await resolveReplyLocale({
+    ctx: options.ctx,
+    repository: options.householdConfigurationRepository
+  })

  if (!telegramUserId || !telegramChatId || !telegramMessageId || !telegramUpdateId) {
-    await options.ctx.reply(t.unableToIdentifyMessage)
+    await options.ctx.reply(
+      getBotTranslations(fallbackLocale).anonymousFeedback.unableToIdentifyMessage
+    )
    return
  }

@@ -167,17 +176,19 @@ async function submitAnonymousFeedback(options: {

  if (memberships.length === 0) {
    await options.promptRepository.clearPendingAction(telegramChatId, telegramUserId)
-    await options.ctx.reply(t.notMember)
+    await options.ctx.reply(getBotTranslations(fallbackLocale).anonymousFeedback.notMember)
    return
  }

  if (memberships.length > 1) {
    await options.promptRepository.clearPendingAction(telegramChatId, telegramUserId)
-    await options.ctx.reply(t.multipleHouseholds)
+    await options.ctx.reply(getBotTranslations(fallbackLocale).anonymousFeedback.multipleHouseholds)
    return
  }

  const member = memberships[0]!
+  const locale = member.preferredLocale ?? member.householdDefaultLocale
+  const t = getBotTranslations(locale).anonymousFeedback
  const householdChat =
    await options.householdConfigurationRepository.getHouseholdChatByHouseholdId(member.householdId)
  const feedbackTopic = await options.householdConfigurationRepository.getHouseholdTopicBinding(
@@ -273,7 +284,10 @@ export function registerAnonymousFeedback(options: {
  logger?: Logger
 }): void {
  options.bot.command('cancel', async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
    const t = getBotTranslations(locale).anonymousFeedback
    if (!isPrivateChat(ctx)) {
      return
@@ -297,7 +311,10 @@ export function registerAnonymousFeedback(options: {
  })

  options.bot.command('anon', async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
    const t = getBotTranslations(locale).anonymousFeedback
    if (!isPrivateChat(ctx)) {
      await ctx.reply(t.useInPrivateChat)
@@ -306,7 +323,11 @@ export function registerAnonymousFeedback(options: {

    const rawText = commandArgText(ctx)
    if (rawText.length === 0) {
-      await startPendingAnonymousFeedbackPrompt(options.promptRepository, ctx)
+      await startPendingAnonymousFeedbackPrompt(
+        options.promptRepository,
+        options.householdConfigurationRepository,
+        ctx
+      )
      return
    }

@@ -351,7 +372,10 @@ export function registerAnonymousFeedback(options: {
  })

  options.bot.callbackQuery(CANCEL_ANONYMOUS_FEEDBACK_CALLBACK, async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
    const t = getBotTranslations(locale).anonymousFeedback
    if (!isPrivateChat(ctx)) {
      await ctx.answerCallbackQuery({
--- a/apps/bot/src/bot-locale.ts
+++ b/apps/bot/src/bot-locale.ts
@@ -0,0 +1,45 @@
+import { normalizeSupportedLocale } from '@household/domain'
+import type { HouseholdConfigurationRepository, HouseholdMemberRecord } from '@household/ports'
+import type { Context } from 'grammy'
+
+import { resolveBotLocale, type BotLocale } from './i18n'
+
+function localeFromMember(member: HouseholdMemberRecord, fallback: BotLocale): BotLocale {
+  return member.preferredLocale ?? member.householdDefaultLocale ?? fallback
+}
+
+export async function resolveReplyLocale(options: {
+  ctx: Pick<Context, 'chat' | 'from'>
+  repository: HouseholdConfigurationRepository | undefined
+  householdId?: string
+}): Promise<BotLocale> {
+  const fallback = resolveBotLocale(options.ctx.from?.language_code)
+  const telegramUserId = options.ctx.from?.id?.toString()
+  const telegramChatId = options.ctx.chat?.id?.toString()
+
+  if (!options.repository) {
+    return fallback
+  }
+
+  if (options.ctx.chat && options.ctx.chat.type !== 'private' && telegramChatId) {
+    const household = await options.repository.getTelegramHouseholdChat(telegramChatId)
+    return household?.defaultLocale ?? fallback
+  }
+
+  if (!telegramUserId) {
+    return fallback
+  }
+
+  if (options.householdId) {
+    const member = await options.repository.getHouseholdMember(options.householdId, telegramUserId)
+    return member ? localeFromMember(member, fallback) : fallback
+  }
+
+  const members = await options.repository.listHouseholdMembersByTelegramUserId(telegramUserId)
+  if (members.length === 1) {
+    return localeFromMember(members[0]!, fallback)
+  }
+
+  const normalized = normalizeSupportedLocale(options.ctx.from?.language_code)
+  return normalized ?? fallback
+}
--- a/apps/bot/src/bot.ts
+++ b/apps/bot/src/bot.ts
@@ -1,19 +1,31 @@
 import { Bot } from 'grammy'
 import type { Logger } from '@household/observability'
+import type { HouseholdConfigurationRepository } from '@household/ports'

-import { botLocaleFromContext, getBotTranslations } from './i18n'
+import { getBotTranslations } from './i18n'
+import { resolveReplyLocale } from './bot-locale'
 import { formatTelegramHelpText } from './telegram-commands'

-export function createTelegramBot(token: string, logger?: Logger): Bot {
+export function createTelegramBot(
+  token: string,
+  logger?: Logger,
+  householdConfigurationRepository?: HouseholdConfigurationRepository
+): Bot {
  const bot = new Bot(token)

  bot.command('help', async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: householdConfigurationRepository
+    })
    await ctx.reply(formatTelegramHelpText(locale))
  })

  bot.command('household_status', async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: householdConfigurationRepository
+    })
    await ctx.reply(getBotTranslations(locale).bot.householdStatusPending)
  })

--- a/apps/bot/src/finance-commands.ts
+++ b/apps/bot/src/finance-commands.ts
@@ -2,7 +2,8 @@ import type { FinanceCommandService } from '@household/application'
 import type { HouseholdConfigurationRepository } from '@household/ports'
 import type { Bot, Context } from 'grammy'

-import { botLocaleFromContext, getBotTranslations } from './i18n'
+import { getBotTranslations } from './i18n'
+import { resolveReplyLocale } from './bot-locale'

 function commandArgs(ctx: Context): string[] {
  const raw = typeof ctx.match === 'string' ? ctx.match.trim() : ''
@@ -24,10 +25,10 @@ export function createFinanceCommandsService(options: {
  register: (bot: Bot) => void
 } {
  function formatStatement(
-    ctx: Context,
+    locale: Parameters<typeof getBotTranslations>[0],
    dashboard: NonNullable<Awaited<ReturnType<FinanceCommandService['generateDashboard']>>>
  ): string {
-    const t = getBotTranslations(botLocaleFromContext(ctx)).finance
+    const t = getBotTranslations(locale).finance

    return [
      t.statementTitle(dashboard.period),
@@ -42,7 +43,11 @@ export function createFinanceCommandsService(options: {
    service: FinanceCommandService
    householdId: string
  } | null> {
-    const t = getBotTranslations(botLocaleFromContext(ctx)).finance
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
+    const t = getBotTranslations(locale).finance
    if (!isGroupChat(ctx)) {
      await ctx.reply(t.useInGroup)
      return null
@@ -63,7 +68,11 @@ export function createFinanceCommandsService(options: {
  }

  async function requireMember(ctx: Context) {
-    const t = getBotTranslations(botLocaleFromContext(ctx)).finance
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
+    const t = getBotTranslations(locale).finance
    const telegramUserId = ctx.from?.id?.toString()
    if (!telegramUserId) {
      await ctx.reply(t.unableToIdentifySender)
@@ -89,7 +98,11 @@ export function createFinanceCommandsService(options: {
  }

  async function requireAdmin(ctx: Context) {
-    const t = getBotTranslations(botLocaleFromContext(ctx)).finance
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
+    const t = getBotTranslations(locale).finance
    const resolved = await requireMember(ctx)
    if (!resolved) {
      return null
@@ -105,7 +118,11 @@ export function createFinanceCommandsService(options: {

  function register(bot: Bot): void {
    bot.command('cycle_open', async (ctx) => {
-      const t = getBotTranslations(botLocaleFromContext(ctx)).finance
+      const locale = await resolveReplyLocale({
+        ctx,
+        repository: options.householdConfigurationRepository
+      })
+      const t = getBotTranslations(locale).finance
      const resolved = await requireAdmin(ctx)
      if (!resolved) {
        return
@@ -126,7 +143,11 @@ export function createFinanceCommandsService(options: {
    })

    bot.command('cycle_close', async (ctx) => {
-      const t = getBotTranslations(botLocaleFromContext(ctx)).finance
+      const locale = await resolveReplyLocale({
+        ctx,
+        repository: options.householdConfigurationRepository
+      })
+      const t = getBotTranslations(locale).finance
      const resolved = await requireAdmin(ctx)
      if (!resolved) {
        return
@@ -146,7 +167,11 @@ export function createFinanceCommandsService(options: {
    })

    bot.command('rent_set', async (ctx) => {
-      const t = getBotTranslations(botLocaleFromContext(ctx)).finance
+      const locale = await resolveReplyLocale({
+        ctx,
+        repository: options.householdConfigurationRepository
+      })
+      const t = getBotTranslations(locale).finance
      const resolved = await requireAdmin(ctx)
      if (!resolved) {
        return
@@ -172,7 +197,11 @@ export function createFinanceCommandsService(options: {
    })

    bot.command('utility_add', async (ctx) => {
-      const t = getBotTranslations(botLocaleFromContext(ctx)).finance
+      const locale = await resolveReplyLocale({
+        ctx,
+        repository: options.householdConfigurationRepository
+      })
+      const t = getBotTranslations(locale).finance
      const resolved = await requireAdmin(ctx)
      if (!resolved) {
        return
@@ -205,7 +234,11 @@ export function createFinanceCommandsService(options: {
    })

    bot.command('statement', async (ctx) => {
-      const t = getBotTranslations(botLocaleFromContext(ctx)).finance
+      const locale = await resolveReplyLocale({
+        ctx,
+        repository: options.householdConfigurationRepository
+      })
+      const t = getBotTranslations(locale).finance
      const resolved = await requireMember(ctx)
      if (!resolved) {
        return
@@ -218,7 +251,7 @@ export function createFinanceCommandsService(options: {
          return
        }

-        await ctx.reply(formatStatement(ctx, dashboard))
+        await ctx.reply(formatStatement(locale, dashboard))
      } catch (error) {
        await ctx.reply(t.statementFailed((error as Error).message))
      }
--- a/apps/bot/src/household-setup.test.ts
+++ b/apps/bot/src/household-setup.test.ts
@@ -147,7 +147,8 @@ describe('registerHouseholdSetupCommands', () => {
          status: 'pending',
          household: {
            id: 'household-1',
-            name: 'Kojori House'
+            name: 'Kojori House',
+            defaultLocale: 'ru'
          }
        }
      }
@@ -236,7 +237,8 @@ describe('registerHouseholdSetupCommands', () => {
          status: 'pending',
          household: {
            id: 'household-1',
-            name: 'Kojori House'
+            name: 'Kojori House',
+            defaultLocale: 'ru'
          }
        }
      }
--- a/apps/bot/src/household-setup.ts
+++ b/apps/bot/src/household-setup.ts
@@ -1,12 +1,15 @@
 import type {
  HouseholdAdminService,
  HouseholdOnboardingService,
-  HouseholdSetupService
+  HouseholdSetupService,
+  HouseholdMiniAppAccess
 } from '@household/application'
 import type { Logger } from '@household/observability'
+import type { HouseholdConfigurationRepository } from '@household/ports'
 import type { Bot, Context } from 'grammy'

-import { botLocaleFromContext, getBotTranslations, type BotLocale } from './i18n'
+import { getBotTranslations, type BotLocale } from './i18n'
+import { resolveReplyLocale } from './bot-locale'

 const APPROVE_MEMBER_CALLBACK_PREFIX = 'approve_member:'

@@ -175,12 +178,17 @@ export function registerHouseholdSetupCommands(options: {
  householdSetupService: HouseholdSetupService
  householdOnboardingService: HouseholdOnboardingService
  householdAdminService: HouseholdAdminService
+  householdConfigurationRepository?: HouseholdConfigurationRepository
  miniAppUrl?: string
  logger?: Logger
 }): void {
  options.bot.command('start', async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
-    const t = getBotTranslations(locale)
+    const fallbackLocale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
+    let locale = fallbackLocale
+    let t = getBotTranslations(locale)

    if (ctx.chat?.type !== 'private') {
      return
@@ -231,6 +239,18 @@ export function registerHouseholdSetupCommands(options: {
      return
    }

+    if (result.status === 'active') {
+      locale = result.member.preferredLocale ?? result.member.householdDefaultLocale
+      t = getBotTranslations(locale)
+    } else {
+      const access = await options.householdOnboardingService.getMiniAppAccess({
+        identity,
+        joinToken
+      })
+      locale = localeFromAccess(access, fallbackLocale)
+      t = getBotTranslations(locale)
+    }
+
    if (result.status === 'active') {
      await ctx.reply(
        t.setup.alreadyActiveMember(result.member.displayName),
@@ -246,8 +266,12 @@ export function registerHouseholdSetupCommands(options: {
  })

  options.bot.command('setup', async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
-    const t = getBotTranslations(locale)
+    const fallbackLocale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
+    let locale = fallbackLocale
+    let t = getBotTranslations(locale)

    if (!isGroupChat(ctx)) {
      await ctx.reply(t.setup.useSetupInGroup)
@@ -278,6 +302,9 @@ export function registerHouseholdSetupCommands(options: {
      return
    }

+    locale = result.household.defaultLocale
+    t = getBotTranslations(locale)
+
    options.logger?.info(
      {
        event: 'household_setup.chat_registered',
@@ -326,7 +353,10 @@ export function registerHouseholdSetupCommands(options: {
  })

  options.bot.command('bind_purchase_topic', async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
    const t = getBotTranslations(locale)

    if (!isGroupChat(ctx)) {
@@ -373,7 +403,10 @@ export function registerHouseholdSetupCommands(options: {
  })

  options.bot.command('bind_feedback_topic', async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
    const t = getBotTranslations(locale)

    if (!isGroupChat(ctx)) {
@@ -420,7 +453,10 @@ export function registerHouseholdSetupCommands(options: {
  })

  options.bot.command('pending_members', async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
    const t = getBotTranslations(locale)

    if (!isGroupChat(ctx)) {
@@ -456,7 +492,10 @@ export function registerHouseholdSetupCommands(options: {
  })

  options.bot.command('approve_member', async (ctx) => {
-    const locale = botLocaleFromContext(ctx)
+    const locale = await resolveReplyLocale({
+      ctx,
+      repository: options.householdConfigurationRepository
+    })
    const t = getBotTranslations(locale)

    if (!isGroupChat(ctx)) {
@@ -493,7 +532,10 @@ export function registerHouseholdSetupCommands(options: {
  options.bot.callbackQuery(
    new RegExp(`^${APPROVE_MEMBER_CALLBACK_PREFIX}(\\d+)$`),
    async (ctx) => {
-      const locale = botLocaleFromContext(ctx)
+      const locale = await resolveReplyLocale({
+        ctx,
+        repository: options.householdConfigurationRepository
+      })
      const t = getBotTranslations(locale)

      if (!isGroupChat(ctx)) {
@@ -554,3 +596,15 @@ export function registerHouseholdSetupCommands(options: {
    }
  )
 }
+
+function localeFromAccess(access: HouseholdMiniAppAccess, fallback: BotLocale): BotLocale {
+  switch (access.status) {
+    case 'active':
+      return access.member.preferredLocale ?? access.member.householdDefaultLocale
+    case 'pending':
+    case 'join_required':
+      return access.household.defaultLocale
+    case 'open_from_group':
+      return fallback
+  }
+}
--- a/apps/bot/src/index.ts
+++ b/apps/bot/src/index.ts
@@ -5,6 +5,7 @@ import {
  createHouseholdAdminService,
  createFinanceCommandService,
  createHouseholdOnboardingService,
+  createLocalePreferenceService,
  createMiniAppAdminService,
  createHouseholdSetupService,
  createReminderJobService
@@ -37,6 +38,7 @@ import {
  createMiniAppApproveMemberHandler,
  createMiniAppPendingMembersHandler
 } from './miniapp-admin'
+import { createMiniAppLocalePreferenceHandler } from './miniapp-locale'

 const runtime = getBotRuntimeConfig()
 configureLogger({
@@ -45,13 +47,16 @@ configureLogger({
 })

 const logger = getLogger('runtime')
-const bot = createTelegramBot(runtime.telegramBotToken, getLogger('telegram'))
-const webhookHandler = webhookCallback(bot, 'std/http')
-
 const shutdownTasks: Array<() => Promise<void>> = []
 const householdConfigurationRepositoryClient = runtime.databaseUrl
  ? createDbHouseholdConfigurationRepository(runtime.databaseUrl)
  : null
+const bot = createTelegramBot(
+  runtime.telegramBotToken,
+  getLogger('telegram'),
+  householdConfigurationRepositoryClient?.repository
+)
+const webhookHandler = webhookCallback(bot, 'std/http')
 const financeRepositoryClients = new Map<string, ReturnType<typeof createDbFinanceRepository>>()
 const financeServices = new Map<string, ReturnType<typeof createFinanceCommandService>>()
 const householdOnboardingService = householdConfigurationRepositoryClient
@@ -62,6 +67,9 @@ const householdOnboardingService = householdConfigurationRepositoryClient
 const miniAppAdminService = householdConfigurationRepositoryClient
  ? createMiniAppAdminService(householdConfigurationRepositoryClient.repository)
  : null
+const localePreferenceService = householdConfigurationRepositoryClient
+  ? createLocalePreferenceService(householdConfigurationRepositoryClient.repository)
+  : null
 const telegramPendingActionRepositoryClient =
  runtime.databaseUrl && runtime.anonymousFeedbackEnabled
    ? createDbTelegramPendingActionRepository(runtime.databaseUrl!)
@@ -168,6 +176,7 @@ if (householdConfigurationRepositoryClient) {
      householdConfigurationRepositoryClient.repository
    ),
    householdOnboardingService: householdOnboardingService!,
+    householdConfigurationRepository: householdConfigurationRepositoryClient.repository,
    ...(runtime.miniAppAllowedOrigins[0]
      ? {
          miniAppUrl: runtime.miniAppAllowedOrigins[0]
@@ -279,6 +288,15 @@ const server = createBotWebhookServer({
        logger: getLogger('miniapp-admin')
      })
    : undefined,
+  miniAppLocalePreference: householdOnboardingService
+    ? createMiniAppLocalePreferenceHandler({
+        allowedOrigins: runtime.miniAppAllowedOrigins,
+        botToken: runtime.telegramBotToken,
+        onboardingService: householdOnboardingService,
+        localePreferenceService: localePreferenceService!,
+        logger: getLogger('miniapp-admin')
+      })
+    : undefined,
  scheduler:
    reminderJobs && runtime.schedulerSharedSecret
      ? {
--- a/apps/bot/src/miniapp-admin.test.ts
+++ b/apps/bot/src/miniapp-admin.test.ts
@@ -18,7 +18,8 @@ function onboardingRepository(): HouseholdConfigurationRepository {
    householdName: 'Kojori House',
    telegramChatId: '-100123',
    telegramChatType: 'supergroup',
-    title: 'Kojori House'
+    title: 'Kojori House',
+    defaultLocale: 'ru' as const
  }

  return {
@@ -52,7 +53,8 @@ function onboardingRepository(): HouseholdConfigurationRepository {
      telegramUserId: input.telegramUserId,
      displayName: input.displayName,
      username: input.username?.trim() || null,
-      languageCode: input.languageCode?.trim() || null
+      languageCode: input.languageCode?.trim() || null,
+      householdDefaultLocale: household.defaultLocale
    }),
    getPendingHouseholdMember: async () => null,
    findPendingHouseholdMemberByTelegramUserId: async () => null,
@@ -61,6 +63,8 @@ function onboardingRepository(): HouseholdConfigurationRepository {
      householdId: household.householdId,
      telegramUserId: input.telegramUserId,
      displayName: input.displayName,
+      preferredLocale: input.preferredLocale ?? null,
+      householdDefaultLocale: household.defaultLocale,
      isAdmin: input.isAdmin === true
    }),
    getHouseholdMember: async () => null,
@@ -73,7 +77,8 @@ function onboardingRepository(): HouseholdConfigurationRepository {
        telegramUserId: '555777',
        displayName: 'Mia',
        username: 'mia',
-        languageCode: 'ru'
+        languageCode: 'ru',
+        householdDefaultLocale: household.defaultLocale
      }
    ],
    approvePendingHouseholdMember: async (input) =>
@@ -83,6 +88,24 @@ function onboardingRepository(): HouseholdConfigurationRepository {
            householdId: household.householdId,
            telegramUserId: '555777',
            displayName: 'Mia',
+            preferredLocale: null,
+            householdDefaultLocale: household.defaultLocale,
+            isAdmin: false
+          }
+        : null,
+    updateHouseholdDefaultLocale: async (_householdId, locale) => ({
+      ...household,
+      defaultLocale: locale
+    }),
+    updateMemberPreferredLocale: async (_householdId, telegramUserId, locale) =>
+      telegramUserId === '555777'
+        ? {
+            id: 'member-555777',
+            householdId: household.householdId,
+            telegramUserId,
+            displayName: 'Mia',
+            preferredLocale: locale,
+            householdDefaultLocale: household.defaultLocale,
            isAdmin: false
          }
        : null
@@ -99,6 +122,8 @@ describe('createMiniAppPendingMembersHandler', () => {
        householdId: 'household-1',
        telegramUserId: '123456',
        displayName: 'Stan',
+        preferredLocale: null,
+        householdDefaultLocale: 'ru',
        isAdmin: true
      }
    ]
@@ -141,7 +166,8 @@ describe('createMiniAppPendingMembersHandler', () => {
          telegramUserId: '555777',
          displayName: 'Mia',
          username: 'mia',
-          languageCode: 'ru'
+          languageCode: 'ru',
+          householdDefaultLocale: 'ru'
        }
      ]
    })
@@ -158,6 +184,8 @@ describe('createMiniAppApproveMemberHandler', () => {
        householdId: 'household-1',
        telegramUserId: '123456',
        displayName: 'Stan',
+        preferredLocale: null,
+        householdDefaultLocale: 'ru',
        isAdmin: true
      }
    ]
@@ -199,6 +227,8 @@ describe('createMiniAppApproveMemberHandler', () => {
        householdId: 'household-1',
        telegramUserId: '555777',
        displayName: 'Mia',
+        preferredLocale: null,
+        householdDefaultLocale: 'ru',
        isAdmin: false
      }
    })
--- a/apps/bot/src/miniapp-auth.test.ts
+++ b/apps/bot/src/miniapp-auth.test.ts
@@ -15,7 +15,8 @@ function onboardingRepository(): HouseholdConfigurationRepository {
    householdName: 'Kojori House',
    telegramChatId: '-100123',
    telegramChatType: 'supergroup',
-    title: 'Kojori House'
+    title: 'Kojori House',
+    defaultLocale: 'ru' as const
  }
  let joinToken: string | null = 'join-token'
  const members = new Map<
@@ -25,6 +26,8 @@ function onboardingRepository(): HouseholdConfigurationRepository {
      householdId: string
      telegramUserId: string
      displayName: string
+      preferredLocale: 'en' | 'ru' | null
+      householdDefaultLocale: 'en' | 'ru'
      isAdmin: boolean
    }
  >()
@@ -35,6 +38,7 @@ function onboardingRepository(): HouseholdConfigurationRepository {
    displayName: string
    username: string | null
    languageCode: string | null
+    householdDefaultLocale: 'ru'
  } | null = null

  return {
@@ -77,7 +81,8 @@ function onboardingRepository(): HouseholdConfigurationRepository {
        telegramUserId: input.telegramUserId,
        displayName: input.displayName,
        username: input.username?.trim() || null,
-        languageCode: input.languageCode?.trim() || null
+        languageCode: input.languageCode?.trim() || null,
+        householdDefaultLocale: household.defaultLocale
      }
      return pending
    },
@@ -89,6 +94,8 @@ function onboardingRepository(): HouseholdConfigurationRepository {
        householdId: household.householdId,
        telegramUserId: input.telegramUserId,
        displayName: input.displayName,
+        preferredLocale: input.preferredLocale ?? null,
+        householdDefaultLocale: household.defaultLocale,
        isAdmin: input.isAdmin === true
      }
      members.set(input.telegramUserId, member)
@@ -112,11 +119,26 @@ function onboardingRepository(): HouseholdConfigurationRepository {
        householdId: household.householdId,
        telegramUserId: pending.telegramUserId,
        displayName: pending.displayName,
+        preferredLocale: null,
+        householdDefaultLocale: household.defaultLocale,
        isAdmin: input.isAdmin === true
      }
      members.set(pending.telegramUserId, member)
      pending = null
      return member
+    },
+    updateHouseholdDefaultLocale: async (_householdId, locale) => ({
+      ...household,
+      defaultLocale: locale
+    }),
+    updateMemberPreferredLocale: async (_householdId, telegramUserId, locale) => {
+      const member = members.get(telegramUserId)
+      return member
+        ? {
+            ...member,
+            preferredLocale: locale
+          }
+        : null
    }
  }
 }
@@ -164,7 +186,9 @@ describe('createMiniAppAuthHandler', () => {
      authorized: true,
      member: {
        displayName: 'Stan',
-        isAdmin: true
+        isAdmin: true,
+        preferredLocale: null,
+        householdDefaultLocale: 'ru'
      },
      telegramUser: {
        id: '123456',
@@ -208,7 +232,8 @@ describe('createMiniAppAuthHandler', () => {
      authorized: false,
      onboarding: {
        status: 'join_required',
-        householdName: 'Kojori House'
+        householdName: 'Kojori House',
+        householdDefaultLocale: 'ru'
      }
    })
  })
@@ -246,7 +271,8 @@ describe('createMiniAppAuthHandler', () => {
      authorized: false,
      onboarding: {
        status: 'pending',
-        householdName: 'Kojori House'
+        householdName: 'Kojori House',
+        householdDefaultLocale: 'ru'
      }
    })
  })
--- a/apps/bot/src/miniapp-auth.ts
+++ b/apps/bot/src/miniapp-auth.ts
@@ -1,4 +1,5 @@
 import type { HouseholdOnboardingService } from '@household/application'
+import type { SupportedLocale } from '@household/domain'
 import type { Logger } from '@household/observability'

 import { verifyTelegramMiniAppInitData } from './telegram-miniapp-auth'
@@ -101,11 +102,14 @@ export interface MiniAppSessionResult {
    householdId: string
    displayName: string
    isAdmin: boolean
+    preferredLocale: SupportedLocale | null
+    householdDefaultLocale: SupportedLocale
  }
  telegramUser?: ReturnType<typeof verifyTelegramMiniAppInitData>
  onboarding?: {
    status: 'join_required' | 'pending' | 'open_from_group'
    householdName?: string
+    householdDefaultLocale?: SupportedLocale
  }
 }

@@ -154,7 +158,8 @@ export function createMiniAppSessionService(options: {
            telegramUser,
            onboarding: {
              status: 'pending',
-              householdName: access.household.name
+              householdName: access.household.name,
+              householdDefaultLocale: access.household.defaultLocale
            }
          }
        case 'join_required':
@@ -163,7 +168,8 @@ export function createMiniAppSessionService(options: {
            telegramUser,
            onboarding: {
              status: 'join_required',
-              householdName: access.household.name
+              householdName: access.household.name,
+              householdDefaultLocale: access.household.defaultLocale
            }
          }
        case 'open_from_group':
@@ -334,7 +340,8 @@ export function createMiniAppJoinHandler(options: {
            authorized: false,
            onboarding: {
              status: 'pending',
-              householdName: result.household.name
+              householdName: result.household.name,
+              householdDefaultLocale: result.household.defaultLocale
            },
            telegramUser
          },
--- a/apps/bot/src/miniapp-dashboard.test.ts
+++ b/apps/bot/src/miniapp-dashboard.test.ts
@@ -76,7 +76,8 @@ function onboardingRepository(): HouseholdConfigurationRepository {
    householdName: 'Kojori House',
    telegramChatId: '-100123',
    telegramChatType: 'supergroup',
-    title: 'Kojori House'
+    title: 'Kojori House',
+    defaultLocale: 'ru' as const
  }

  return {
@@ -110,7 +111,8 @@ function onboardingRepository(): HouseholdConfigurationRepository {
      telegramUserId: input.telegramUserId,
      displayName: input.displayName,
      username: input.username?.trim() || null,
-      languageCode: input.languageCode?.trim() || null
+      languageCode: input.languageCode?.trim() || null,
+      householdDefaultLocale: household.defaultLocale
    }),
    getPendingHouseholdMember: async () => null,
    findPendingHouseholdMemberByTelegramUserId: async () => null,
@@ -119,13 +121,20 @@ function onboardingRepository(): HouseholdConfigurationRepository {
      householdId: household.householdId,
      telegramUserId: input.telegramUserId,
      displayName: input.displayName,
+      preferredLocale: input.preferredLocale ?? null,
+      householdDefaultLocale: household.defaultLocale,
      isAdmin: input.isAdmin === true
    }),
    getHouseholdMember: async () => null,
    listHouseholdMembers: async () => [],
    listHouseholdMembersByTelegramUserId: async () => [],
    listPendingHouseholdMembers: async () => [],
-    approvePendingHouseholdMember: async () => null
+    approvePendingHouseholdMember: async () => null,
+    updateHouseholdDefaultLocale: async (_householdId, locale) => ({
+      ...household,
+      defaultLocale: locale
+    }),
+    updateMemberPreferredLocale: async () => null
  }
 }

@@ -147,6 +156,8 @@ describe('createMiniAppDashboardHandler', () => {
        householdId: 'household-1',
        telegramUserId: '123456',
        displayName: 'Stan',
+        preferredLocale: null,
+        householdDefaultLocale: 'ru',
        isAdmin: true
      }
    ]
@@ -223,6 +234,8 @@ describe('createMiniAppDashboardHandler', () => {
        householdId: 'household-1',
        telegramUserId: '123456',
        displayName: 'Stan',
+        preferredLocale: null,
+        householdDefaultLocale: 'ru',
        isAdmin: true
      }
    ]
--- a/apps/bot/src/miniapp-locale.test.ts
+++ b/apps/bot/src/miniapp-locale.test.ts
@@ -0,0 +1,212 @@
+import { describe, expect, test } from 'bun:test'
+
+import {
+  createHouseholdOnboardingService,
+  createLocalePreferenceService
+} from '@household/application'
+import type {
+  HouseholdConfigurationRepository,
+  HouseholdMemberRecord,
+  HouseholdTopicBindingRecord
+} from '@household/ports'
+
+import { createMiniAppLocalePreferenceHandler } from './miniapp-locale'
+import { buildMiniAppInitData } from './telegram-miniapp-test-helpers'
+
+function repository(): HouseholdConfigurationRepository {
+  const household = {
+    householdId: 'household-1',
+    householdName: 'Kojori House',
+    telegramChatId: '-100123',
+    telegramChatType: 'supergroup',
+    title: 'Kojori House',
+    defaultLocale: 'ru' as 'en' | 'ru'
+  }
+
+  const members = new Map<string, HouseholdMemberRecord>([
+    [
+      '123456',
+      {
+        id: 'member-123456',
+        householdId: household.householdId,
+        telegramUserId: '123456',
+        displayName: 'Stan',
+        preferredLocale: null,
+        householdDefaultLocale: household.defaultLocale,
+        isAdmin: true
+      }
+    ],
+    [
+      '222222',
+      {
+        id: 'member-222222',
+        householdId: household.householdId,
+        telegramUserId: '222222',
+        displayName: 'Mia',
+        preferredLocale: null,
+        householdDefaultLocale: household.defaultLocale,
+        isAdmin: false
+      }
+    ]
+  ])
+
+  return {
+    registerTelegramHouseholdChat: async () => ({ status: 'existing', household }),
+    getTelegramHouseholdChat: async () => household,
+    getHouseholdChatByHouseholdId: async () => household,
+    bindHouseholdTopic: async (input) =>
+      ({
+        householdId: input.householdId,
+        role: input.role,
+        telegramThreadId: input.telegramThreadId,
+        topicName: input.topicName?.trim() || null
+      }) satisfies HouseholdTopicBindingRecord,
+    getHouseholdTopicBinding: async () => null,
+    findHouseholdTopicByTelegramContext: async () => null,
+    listHouseholdTopicBindings: async () => [],
+    upsertHouseholdJoinToken: async () => ({
+      householdId: household.householdId,
+      householdName: household.householdName,
+      token: 'join-token',
+      createdByTelegramUserId: null
+    }),
+    getHouseholdJoinToken: async () => null,
+    getHouseholdByJoinToken: async () => null,
+    upsertPendingHouseholdMember: async (input) => ({
+      householdId: input.householdId,
+      householdName: household.householdName,
+      telegramUserId: input.telegramUserId,
+      displayName: input.displayName,
+      username: input.username?.trim() || null,
+      languageCode: input.languageCode?.trim() || null,
+      householdDefaultLocale: household.defaultLocale
+    }),
+    getPendingHouseholdMember: async () => null,
+    findPendingHouseholdMemberByTelegramUserId: async () => null,
+    ensureHouseholdMember: async (input) =>
+      members.get(input.telegramUserId) ?? {
+        id: `member-${input.telegramUserId}`,
+        householdId: input.householdId,
+        telegramUserId: input.telegramUserId,
+        displayName: input.displayName,
+        preferredLocale: input.preferredLocale ?? null,
+        householdDefaultLocale: household.defaultLocale,
+        isAdmin: input.isAdmin === true
+      },
+    getHouseholdMember: async (_householdId, telegramUserId) => members.get(telegramUserId) ?? null,
+    listHouseholdMembers: async () => [...members.values()],
+    listHouseholdMembersByTelegramUserId: async (telegramUserId) => {
+      const member = members.get(telegramUserId)
+      return member ? [member] : []
+    },
+    listPendingHouseholdMembers: async () => [],
+    approvePendingHouseholdMember: async () => null,
+    updateHouseholdDefaultLocale: async (_householdId, locale) => {
+      household.defaultLocale = locale
+      for (const [id, member] of members.entries()) {
+        members.set(id, {
+          ...member,
+          householdDefaultLocale: locale
+        })
+      }
+      return household
+    },
+    updateMemberPreferredLocale: async (_householdId, telegramUserId, locale) => {
+      const member = members.get(telegramUserId)
+      if (!member) {
+        return null
+      }
+
+      const next = {
+        ...member,
+        preferredLocale: locale
+      }
+      members.set(telegramUserId, next)
+      return next
+    }
+  }
+}
+
+describe('createMiniAppLocalePreferenceHandler', () => {
+  test('updates member locale preference', async () => {
+    const authDate = Math.floor(Date.now() / 1000)
+    const householdRepository = repository()
+    const handler = createMiniAppLocalePreferenceHandler({
+      allowedOrigins: ['http://localhost:5173'],
+      botToken: 'test-bot-token',
+      onboardingService: createHouseholdOnboardingService({
+        repository: householdRepository
+      }),
+      localePreferenceService: createLocalePreferenceService(householdRepository)
+    })
+
+    const response = await handler.handler(
+      new Request('http://localhost/api/miniapp/preferences/locale', {
+        method: 'POST',
+        headers: {
+          origin: 'http://localhost:5173',
+          'content-type': 'application/json'
+        },
+        body: JSON.stringify({
+          initData: buildMiniAppInitData('test-bot-token', authDate, {
+            id: 123456,
+            first_name: 'Stan',
+            language_code: 'ru'
+          }),
+          locale: 'en',
+          scope: 'member'
+        })
+      })
+    )
+
+    expect(response.status).toBe(200)
+    expect(await response.json()).toEqual({
+      ok: true,
+      authorized: true,
+      locale: {
+        scope: 'member',
+        effectiveLocale: 'en',
+        memberPreferredLocale: 'en',
+        householdDefaultLocale: 'ru'
+      }
+    })
+  })
+
+  test('rejects household locale updates for non-admin members', async () => {
+    const authDate = Math.floor(Date.now() / 1000)
+    const householdRepository = repository()
+    const handler = createMiniAppLocalePreferenceHandler({
+      allowedOrigins: ['http://localhost:5173'],
+      botToken: 'test-bot-token',
+      onboardingService: createHouseholdOnboardingService({
+        repository: householdRepository
+      }),
+      localePreferenceService: createLocalePreferenceService(householdRepository)
+    })
+
+    const response = await handler.handler(
+      new Request('http://localhost/api/miniapp/preferences/locale', {
+        method: 'POST',
+        headers: {
+          origin: 'http://localhost:5173',
+          'content-type': 'application/json'
+        },
+        body: JSON.stringify({
+          initData: buildMiniAppInitData('test-bot-token', authDate, {
+            id: 222222,
+            first_name: 'Mia',
+            language_code: 'ru'
+          }),
+          locale: 'en',
+          scope: 'household'
+        })
+      })
+    )
+
+    expect(response.status).toBe(403)
+    expect(await response.json()).toEqual({
+      ok: false,
+      error: 'Admin access required'
+    })
+  })
+})
--- a/apps/bot/src/miniapp-locale.ts
+++ b/apps/bot/src/miniapp-locale.ts
@@ -0,0 +1,150 @@
+import type { HouseholdOnboardingService, LocalePreferenceService } from '@household/application'
+import { normalizeSupportedLocale } from '@household/domain'
+import type { Logger } from '@household/observability'
+
+import {
+  allowedMiniAppOrigin,
+  createMiniAppSessionService,
+  miniAppErrorResponse,
+  miniAppJsonResponse
+} from './miniapp-auth'
+
+interface LocalePreferenceRequest {
+  initData: string
+  locale: 'en' | 'ru'
+  scope: 'member' | 'household'
+}
+
+async function readLocalePreferenceRequest(request: Request): Promise<LocalePreferenceRequest> {
+  const text = await request.text()
+  if (text.trim().length === 0) {
+    throw new Error('Missing initData')
+  }
+
+  let parsed: { initData?: string; locale?: string; scope?: string }
+  try {
+    parsed = JSON.parse(text) as { initData?: string; locale?: string; scope?: string }
+  } catch {
+    throw new Error('Invalid JSON body')
+  }
+
+  const initData = parsed.initData?.trim()
+  if (!initData) {
+    throw new Error('Missing initData')
+  }
+
+  const locale = normalizeSupportedLocale(parsed.locale)
+  if (!locale) {
+    throw new Error('Invalid locale')
+  }
+
+  const scope = parsed.scope?.trim()
+  if (scope !== 'member' && scope !== 'household') {
+    throw new Error('Invalid locale scope')
+  }
+
+  return {
+    initData,
+    locale,
+    scope
+  }
+}
+
+export function createMiniAppLocalePreferenceHandler(options: {
+  allowedOrigins: readonly string[]
+  botToken: string
+  onboardingService: HouseholdOnboardingService
+  localePreferenceService: LocalePreferenceService
+  logger?: Logger
+}): {
+  handler: (request: Request) => Promise<Response>
+} {
+  const sessionService = createMiniAppSessionService({
+    botToken: options.botToken,
+    onboardingService: options.onboardingService
+  })
+
+  return {
+    handler: async (request) => {
+      const origin = allowedMiniAppOrigin(request, options.allowedOrigins)
+
+      if (request.method === 'OPTIONS') {
+        return miniAppJsonResponse({ ok: true }, 204, origin)
+      }
+
+      if (request.method !== 'POST') {
+        return miniAppJsonResponse({ ok: false, error: 'Method Not Allowed' }, 405, origin)
+      }
+
+      try {
+        const payload = await readLocalePreferenceRequest(request)
+        const session = await sessionService.authenticate({
+          initData: payload.initData
+        })
+
+        if (!session) {
+          return miniAppJsonResponse(
+            { ok: false, error: 'Invalid Telegram init data' },
+            401,
+            origin
+          )
+        }
+
+        if (!session.authorized || !session.member || !session.telegramUser) {
+          return miniAppJsonResponse(
+            { ok: false, error: 'Access limited to active household members' },
+            403,
+            origin
+          )
+        }
+
+        let memberPreferredLocale = session.member.preferredLocale
+        let householdDefaultLocale = session.member.householdDefaultLocale
+
+        if (payload.scope === 'member') {
+          const result = await options.localePreferenceService.updateMemberLocale({
+            householdId: session.member.householdId,
+            telegramUserId: session.telegramUser.id,
+            locale: payload.locale
+          })
+
+          if (result.status === 'rejected') {
+            return miniAppJsonResponse({ ok: false, error: 'Member not found' }, 404, origin)
+          }
+
+          memberPreferredLocale = result.member.preferredLocale
+          householdDefaultLocale = result.member.householdDefaultLocale
+        } else {
+          const result = await options.localePreferenceService.updateHouseholdLocale({
+            householdId: session.member.householdId,
+            actorIsAdmin: session.member.isAdmin,
+            locale: payload.locale
+          })
+
+          if (result.status === 'rejected') {
+            return miniAppJsonResponse({ ok: false, error: 'Admin access required' }, 403, origin)
+          }
+
+          householdDefaultLocale = result.household.defaultLocale
+        }
+
+        return miniAppJsonResponse(
+          {
+            ok: true,
+            authorized: true,
+            locale: {
+              scope: payload.scope,
+              effectiveLocale: memberPreferredLocale ?? householdDefaultLocale,
+              memberPreferredLocale,
+              householdDefaultLocale
+            }
+          },
+          200,
+          origin
+        )
+      } catch (error) {
+        return miniAppErrorResponse(error, origin, options.logger)
+      }
+    }
+  }
+}
--- a/apps/bot/src/purchase-topic-ingestion.ts
+++ b/apps/bot/src/purchase-topic-ingestion.ts
@@ -9,7 +9,7 @@ import type {
 } from '@household/ports'

 import { createDbClient, schema } from '@household/db'
-import { botLocaleFromContext, getBotTranslations, type BotLocale } from './i18n'
+import { getBotTranslations, type BotLocale } from './i18n'

 export interface PurchaseTopicIngestionConfig {
  householdId: string
@@ -325,7 +325,7 @@ export function registerPurchaseTopicIngestion(

    try {
      const status = await repository.save(record, options.llmFallback)
-      const acknowledgement = buildPurchaseAcknowledgement(status, botLocaleFromContext(ctx))
+      const acknowledgement = buildPurchaseAcknowledgement(status, 'en')

      if (status.status === 'created') {
        options.logger?.info(
@@ -395,7 +395,13 @@ export function registerConfiguredPurchaseTopicIngestion(

    try {
      const status = await repository.save(record, options.llmFallback)
-      const acknowledgement = buildPurchaseAcknowledgement(status, botLocaleFromContext(ctx))
+      const householdChat = await householdConfigurationRepository.getHouseholdChatByHouseholdId(
+        record.householdId
+      )
+      const acknowledgement = buildPurchaseAcknowledgement(
+        status,
+        householdChat?.defaultLocale ?? 'en'
+      )

      if (status.status === 'created') {
        options.logger?.info(
--- a/apps/bot/src/server.ts
+++ b/apps/bot/src/server.ts
@@ -32,6 +32,12 @@ export interface BotWebhookServerOptions {
        handler: (request: Request) => Promise<Response>
      }
    | undefined
+  miniAppLocalePreference?:
+    | {
+        path?: string
+        handler: (request: Request) => Promise<Response>
+      }
+    | undefined
  scheduler?:
    | {
        pathPrefix?: string
@@ -69,6 +75,8 @@ export function createBotWebhookServer(options: BotWebhookServerOptions): {
    options.miniAppPendingMembers?.path ?? '/api/miniapp/admin/pending-members'
  const miniAppApproveMemberPath =
    options.miniAppApproveMember?.path ?? '/api/miniapp/admin/approve-member'
+  const miniAppLocalePreferencePath =
+    options.miniAppLocalePreference?.path ?? '/api/miniapp/preferences/locale'
  const schedulerPathPrefix = options.scheduler
    ? (options.scheduler.pathPrefix ?? '/jobs/reminder')
    : null
@@ -101,6 +109,10 @@ export function createBotWebhookServer(options: BotWebhookServerOptions): {
        return await options.miniAppApproveMember.handler(request)
      }

+      if (options.miniAppLocalePreference && url.pathname === miniAppLocalePreferencePath) {
+        return await options.miniAppLocalePreference.handler(request)
+      }
+
      if (url.pathname !== normalizedWebhookPath) {
        if (schedulerPathPrefix && url.pathname.startsWith(`${schedulerPathPrefix}/`)) {
          if (request.method !== 'POST') {
--- a/apps/miniapp/src/App.tsx
+++ b/apps/miniapp/src/App.tsx
@@ -7,6 +7,7 @@ import {
  fetchMiniAppPendingMembers,
  fetchMiniAppSession,
  joinMiniAppHousehold,
+  updateMiniAppLocalePreference,
  type MiniAppDashboard,
  type MiniAppPendingMember
 } from './miniapp-api'
@@ -36,6 +37,8 @@ type SessionState =
      member: {
        displayName: string
        isAdmin: boolean
+        preferredLocale: Locale | null
+        householdDefaultLocale: Locale
      }
      telegramUser: {
        firstName: string | null
@@ -51,7 +54,9 @@ const demoSession: Extract<SessionState, { status: 'ready' }> = {
  mode: 'demo',
  member: {
    displayName: 'Demo Resident',
-    isAdmin: false
+    isAdmin: false,
+    preferredLocale: 'en',
+    householdDefaultLocale: 'en'
  },
  telegramUser: {
    firstName: 'Demo',
@@ -112,6 +117,8 @@ function App() {
  const [pendingMembers, setPendingMembers] = createSignal<readonly MiniAppPendingMember[]>([])
  const [joining, setJoining] = createSignal(false)
  const [approvingTelegramUserId, setApprovingTelegramUserId] = createSignal<string | null>(null)
+  const [savingMemberLocale, setSavingMemberLocale] = createSignal(false)
+  const [savingHouseholdLocale, setSavingHouseholdLocale] = createSignal(false)

  const copy = createMemo(() => dictionary[locale()])
  const onboardingSession = createMemo(() => {
@@ -153,7 +160,8 @@ function App() {
  }

  async function bootstrap() {
-    setLocale(detectLocale())
+    const fallbackLocale = detectLocale()
+    setLocale(fallbackLocale)

    webApp?.ready?.()
    webApp?.expand?.()
@@ -175,6 +183,10 @@ function App() {
    try {
      const payload = await fetchMiniAppSession(initData, joinContext().joinToken)
      if (!payload.authorized || !payload.member || !payload.telegramUser) {
+        setLocale(
+          payload.onboarding?.householdDefaultLocale ??
+            ((payload.telegramUser?.languageCode ?? fallbackLocale).startsWith('ru') ? 'ru' : 'en')
+        )
        setSession({
          status: 'onboarding',
          mode: payload.onboarding?.status ?? 'open_from_group',
@@ -192,6 +204,7 @@ function App() {
        return
      }

+      setLocale(payload.member.preferredLocale ?? payload.member.householdDefaultLocale)
      setSession({
        status: 'ready',
        mode: 'live',
@@ -284,6 +297,7 @@ function App() {
    try {
      const payload = await joinMiniAppHousehold(initData, joinToken)
      if (payload.authorized && payload.member && payload.telegramUser) {
+        setLocale(payload.member.preferredLocale ?? payload.member.householdDefaultLocale)
        setSession({
          status: 'ready',
          mode: 'live',
@@ -297,6 +311,10 @@ function App() {
        return
      }

+      setLocale(
+        payload.onboarding?.householdDefaultLocale ??
+          ((payload.telegramUser?.languageCode ?? locale()).startsWith('ru') ? 'ru' : 'en')
+      )
      setSession({
        status: 'onboarding',
        mode: payload.onboarding?.status ?? 'pending',
@@ -339,6 +357,71 @@ function App() {
    }
  }

+  async function handleMemberLocaleChange(nextLocale: Locale) {
+    const initData = webApp?.initData?.trim()
+    const currentReady = readySession()
+
+    setLocale(nextLocale)
+
+    if (!initData || currentReady?.mode !== 'live') {
+      return
+    }
+
+    setSavingMemberLocale(true)
+
+    try {
+      const updated = await updateMiniAppLocalePreference(initData, nextLocale, 'member')
+
+      setSession((current) =>
+        current.status === 'ready'
+          ? {
+              ...current,
+              member: {
+                ...current.member,
+                preferredLocale: updated.memberPreferredLocale,
+                householdDefaultLocale: updated.householdDefaultLocale
+              }
+            }
+          : current
+      )
+      setLocale(updated.effectiveLocale)
+    } finally {
+      setSavingMemberLocale(false)
+    }
+  }
+
+  async function handleHouseholdLocaleChange(nextLocale: Locale) {
+    const initData = webApp?.initData?.trim()
+    const currentReady = readySession()
+    if (!initData || currentReady?.mode !== 'live' || !currentReady.member.isAdmin) {
+      return
+    }
+
+    setSavingHouseholdLocale(true)
+
+    try {
+      const updated = await updateMiniAppLocalePreference(initData, nextLocale, 'household')
+
+      setSession((current) =>
+        current.status === 'ready'
+          ? {
+              ...current,
+              member: {
+                ...current.member,
+                householdDefaultLocale: updated.householdDefaultLocale
+              }
+            }
+          : current
+      )
+
+      if (!currentReady.member.preferredLocale) {
+        setLocale(updated.effectiveLocale)
+      }
+    } finally {
+      setSavingHouseholdLocale(false)
+    }
+  }
+
  const renderPanel = () => {
    switch (activeNav()) {
      case 'balances':
@@ -396,6 +479,34 @@ function App() {
      case 'house':
        return readySession()?.member.isAdmin ? (
          <div class="balance-list">
+            <article class="balance-item">
+              <header>
+                <strong>{copy().householdLanguage}</strong>
+                <span>{readySession()?.member.householdDefaultLocale.toUpperCase()}</span>
+              </header>
+              <div class="locale-switch__buttons">
+                <button
+                  classList={{
+                    'is-active': readySession()?.member.householdDefaultLocale === 'en'
+                  }}
+                  type="button"
+                  disabled={savingHouseholdLocale()}
+                  onClick={() => void handleHouseholdLocaleChange('en')}
+                >
+                  EN
+                </button>
+                <button
+                  classList={{
+                    'is-active': readySession()?.member.householdDefaultLocale === 'ru'
+                  }}
+                  type="button"
+                  disabled={savingHouseholdLocale()}
+                  onClick={() => void handleHouseholdLocaleChange('ru')}
+                >
+                  RU
+                </button>
+              </div>
+            </article>
            <article class="balance-item">
              <header>
                <strong>{copy().pendingMembersTitle}</strong>
@@ -470,14 +581,16 @@ function App() {
            <button
              classList={{ 'is-active': locale() === 'en' }}
              type="button"
-              onClick={() => setLocale('en')}
+              disabled={savingMemberLocale()}
+              onClick={() => void handleMemberLocaleChange('en')}
            >
              EN
            </button>
            <button
              classList={{ 'is-active': locale() === 'ru' }}
              type="button"
-              onClick={() => setLocale('ru')}
+              disabled={savingMemberLocale()}
+              onClick={() => void handleMemberLocaleChange('ru')}
            >
              RU
            </button>
--- a/apps/miniapp/src/i18n.ts
+++ b/apps/miniapp/src/i18n.ts
@@ -27,6 +27,8 @@ export const dictionary = {
      'The real session gate needs Telegram mini app data. Local development falls back to a preview shell.',
    reload: 'Retry',
    language: 'Language',
+    householdLanguage: 'Household language',
+    savingLanguage: 'Saving…',
    home: 'Home',
    balances: 'Balances',
    ledger: 'Ledger',
@@ -90,6 +92,8 @@ export const dictionary = {
      'Настоящая проверка требует данные Telegram Mini App. Локально показывается демо-оболочка.',
    reload: 'Повторить',
    language: 'Язык',
+    householdLanguage: 'Язык дома',
+    savingLanguage: 'Сохраняем…',
    home: 'Главная',
    balances: 'Баланс',
    ledger: 'Леджер',
--- a/apps/miniapp/src/miniapp-api.ts
+++ b/apps/miniapp/src/miniapp-api.ts
@@ -5,6 +5,8 @@ export interface MiniAppSession {
  member?: {
    displayName: string
    isAdmin: boolean
+    preferredLocale: 'en' | 'ru' | null
+    householdDefaultLocale: 'en' | 'ru'
  }
  telegramUser?: {
    firstName: string | null
@@ -14,9 +16,17 @@ export interface MiniAppSession {
  onboarding?: {
    status: 'join_required' | 'pending' | 'open_from_group'
    householdName?: string
+    householdDefaultLocale?: 'en' | 'ru'
  }
 }

+export interface MiniAppLocalePreference {
+  scope: 'member' | 'household'
+  effectiveLocale: 'en' | 'ru'
+  memberPreferredLocale: 'en' | 'ru' | null
+  householdDefaultLocale: 'en' | 'ru'
+}
+
 export interface MiniAppPendingMember {
  telegramUserId: string
  displayName: string
@@ -219,3 +229,34 @@ export async function approveMiniAppPendingMember(
    throw new Error(payload.error ?? 'Failed to approve member')
  }
 }
+
+export async function updateMiniAppLocalePreference(
+  initData: string,
+  locale: 'en' | 'ru',
+  scope: 'member' | 'household'
+): Promise<MiniAppLocalePreference> {
+  const response = await fetch(`${apiBaseUrl()}/api/miniapp/preferences/locale`, {
+    method: 'POST',
+    headers: {
+      'content-type': 'application/json'
+    },
+    body: JSON.stringify({
+      initData,
+      locale,
+      scope
+    })
+  })
+
+  const payload = (await response.json()) as {
+    ok: boolean
+    authorized?: boolean
+    locale?: MiniAppLocalePreference
+    error?: string
+  }
+
+  if (!response.ok || !payload.authorized || !payload.locale) {
+    throw new Error(payload.error ?? 'Failed to update locale preference')
+  }
+
+  return payload.locale
+}