diff --git a/plugin-designs/posterverse/posterverse.vue b/plugin-designs/posterverse/posterverse.vue
index 0e2100807..ccb34e9c7 100644
--- a/plugin-designs/posterverse/posterverse.vue
+++ b/plugin-designs/posterverse/posterverse.vue
@@ -57,6 +57,11 @@
       </template>
     </section>
 
+    <!-- The language menu: the end of the phone bar, and the bottom of the desktop rail. A pick asks the
+         host first (doxa-language-request); only an uncancelled pick reaches setLocale. -->
+    <template #phone-end><ShellLanguageMenu :current="uiLocale" @switch="setLocale" /></template>
+    <template #rail-end="{ collapsed }"><ShellLanguageMenu :current="uiLocale" :collapsed="collapsed" @switch="setLocale" /></template>
+
     <!-- The pane is the scroller (overflow-y:auto), so back-to-top follows the active pane. -->
     <BackToTopButton :target="activePaneEl" :labels="{ backToTop: tr('backToTop') }" />
   </VerticalTabsLayout>
@@ -66,6 +71,8 @@
 import { defineComponent, inject } from 'vue'
 import VerticalTabsLayout from '@map/layouts/VerticalTabsLayout.vue'
 import BackToTopButton from '@map/components/BackToTopButton.vue'
+import ShellLanguageMenu from '@map/components/ShellLanguageMenu.vue'
+import { saveLocale } from '@map/layouts/app-wrapper-material/languages.js'
 import { loadScriptOnce, whenTagDefined } from '@map/utils/embedScript.js'
 import { translate, LOCALES } from './src/strings.js'
 import { SECTIONS, TABS, resolveTabs } from './src/tabs.js'
@@ -93,7 +100,7 @@ export default defineComponent({
   // The host's attributes stay on the host: an inline style copied onto the layout root beats the
   // layout's own rules (a styled host once collapsed a nested map to 76px).
   inheritAttrs: false,
-  components: { VerticalTabsLayout, BackToTopButton },
+  components: { VerticalTabsLayout, BackToTopButton, ShellLanguageMenu },
   props: {
     treeBase: { type: String, default: '' },
     profileConfig: { type: [String, Object], default: '' },
@@ -128,6 +135,11 @@ export default defineComponent({
       // The manifest's `runtime` block (the build's apiBaseUrl + public token), for foreign-page embeds.
       runtime: {},
       hostLang: detectHostLocale(),
+      // A language picked in THIS session through the menu, and the host's language value it was picked
+      // over. The pick wins only while that value is unchanged; the saved choice (loadLocale) is never
+      // read, since it falls back to the browser's language and would override the host page.
+      localPick: '',
+      pickBase: null,
       // Until the manifest lands, the rail shows the rows that are expected to exist; provisional rows
       // appear only once the manifest proves their bundle is in this tree.
       tabs: TABS.filter((d) => !d.provisional).map(freshTab),
@@ -153,10 +165,13 @@ export default defineComponent({
       return this.manifestBase ? this.manifestBase.replace(/\/+$/, '') + '/assets' : ''
     },
     headingText() { return String(this.cfg.heading || this.heading || '').trim() || 'Posterverse' },
-    // Language precedence: what the host says, then the host page's own language, then English.
+    // The language the host passed: the `language` prop, else profile-config language / locale / lang.
+    hostLanguage() { return String(this.language || this.cfg.language || this.cfg.locale || this.cfg.lang || '').trim() },
+    // Language precedence: this session's menu pick (while the host's value is the one it was made over),
+    // then what the host says, then the host page's own language, then English.
     effectiveLocale() {
-      const fromProp = String(this.language || this.cfg.language || this.cfg.locale || this.cfg.lang || '').trim()
-      return (fromProp || this.hostLang || 'en').split('-')[0].toLowerCase()
+      if (this.localPick && this.hostLanguage === this.pickBase) return this.localPick
+      return (this.hostLanguage || this.hostLang || 'en').split('-')[0].toLowerCase()
     },
     uiLocale() { return LOCALES.includes(this.effectiveLocale) ? this.effectiveLocale : 'en' },
     uiDir() { return this.uiLocale === 'ar' ? 'rtl' : 'ltr' },
@@ -201,6 +216,8 @@ export default defineComponent({
       this.mountElement(this.activeIndex)
     },
     tab(id) { if (id) this.onSelect(id) },
+    // A host that sets a new language takes over again: the session pick is dropped.
+    hostLanguage(v) { if (v !== this.pickBase) { this.localPick = ''; this.pickBase = null } },
   },
   mounted() {
     this.watchHostLang()
@@ -213,6 +230,12 @@ export default defineComponent({
   },
   methods: {
     tr(key, params) { return translate(this.uiLocale, key, params) },
+    // The menu's 'switch': no host cancelled the request, so the shell switches itself.
+    setLocale(code) {
+      this.pickBase = this.hostLanguage
+      this.localPick = code
+      saveLocale(code)
+    },
     tabLabel(t) { return this.tr('tab.' + t.id) },
     tabSub(t) { return t.section === 'experimental' ? this.tr('experimentalSub') : this.tr('sub.' + t.id) },
     setSlot(i, el) { if (el) this._slots = Object.assign(this._slots || {}, { [i]: el }) },