[Unplugin-vue-i18n] Problem with translating nested keys (flat json)

[nao237854]

Reporting a bug?

Hi,
I'm having trouble translating nested keys.
I have two keys: "navBar.orders" and "navBar.orders.buy." "navBar.orders" translates properly, but "navBar.orders.buy" doesn't.
However, when I change "navBar.orders" to "navBar.orders.orders," "navBar.orders.buy" translates correctly.
Is this intentional? Everything works well without the unplugin-vue-i18n.

en.json

  "navBar.orders": "Test",
  "navBar.orders.buy": "Test2",

import { useI18n } from 'vue-i18n'
const i18n = useI18n()
console.log(i18n.t('navBar.orders')) // Test
console.log(i18n.t('navBar.orders.buy')) //navBar.orders.buy

---

en.json

  "navBar.orders.orders": "Test",
  "navBar.orders.buy": "Test2",

import { useI18n } from 'vue-i18n'
const i18n = useI18n()
console.log(i18n.t('navBar.orders.orders')) // Test
console.log(i18n.t('navBar.orders.buy')) // Test2

Expected behavior

import { useI18n } from 'vue-i18n'
const i18n = useI18n()
console.log(i18n.t('navBar.orders')) // Test
console.log(i18n.t('navBar.orders.buy')) //Test2

Reproduction

i18n.ts

import { createI18n } from 'vue-i18n'
import messages from '@intlify/unplugin-vue-i18n/messages'

const i18n = createI18n({
    legacy: false,
    locale: 'pl',
    fallbackLocale: 'pl',
    messages,
    flatJson: true,
    warnHtmlInMessage: 'off',
    globalInjection: true,
  });

vite.config.ts

      VueI18nPlugin({
        /* options */
        // locale messages resource pre-compile option
        include: resolve(dirname(fileURLToPath(import.meta.url)), 'src/locales/**'),
        strictMessage: false,
        escapeHtml: true,
        dropMessageCompiler: true,
      }),

en.json

  "navBar.orders": "Test",
  "navBar.orders.buy": "Test2",

import { useI18n } from 'vue-i18n'
const i18n = useI18n()
console.log(i18n.t('navBar.orders')) // Test
console.log(i18n.t('navBar.orders.buy')) //navBar.orders.buy

Issue Package

unplugin-vue-i18n

System Info

System:
    OS: Linux 6.6 Ubuntu 24.04.2 LTS 24.04.2 LTS (Noble Numbat)
    CPU: (24) x64 13th Gen Intel(R) Core(TM) i7-13700K
    Memory: 26.77 GB / 31.22 GB
    Container: Yes
    Shell: 5.9 - /usr/bin/zsh
  Binaries:
    Node: 24.3.0 - ~/.nvm/versions/node/v24.3.0/bin/node
    npm: 11.4.2 - ~/.nvm/versions/node/v24.3.0/bin/npm
  npmPackages:
    rolldown-vite:  7.0.5 
    vue: ^3.5.17 => 3.5.17 
    vue-i18n: ^11.1.9 => 11.1.9

Screenshot

No response

Additional context

No response

Validations

• Read the Contributing Guidelines.
• Read the README
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion.