diff --git a/plugin-designs/posterverse/posterverse.vue b/plugin-designs/posterverse/posterverse.vue
index f1c5322e2..07cd781ad 100644
--- a/plugin-designs/posterverse/posterverse.vue
+++ b/plugin-designs/posterverse/posterverse.vue
@@ -74,7 +74,7 @@ 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 { readViewKeys, writeViewKeys, onAddressChange, urlOwnerOf, ownAddress } from '@map/composables/useViewAddress.js'
+import { readViewKeys, claimView, onAddressChange, urlOwnerOf, ownAddress, depthOf, subtabAt } from '@map/composables/useViewAddress.js'
 import { translate, LOCALES } from './src/strings.js'
 import { SECTIONS, TABS, resolveTabs } from './src/tabs.js'
 
@@ -236,9 +236,11 @@ export default defineComponent({
     // A nested plugin's choice inside a tab (?pane=, ?place=) reaches the address through the owner: recorded
     // only while this page owns its address, never a tab switch, and the event stops here.
     this._offOwn = ownAddress(this.$el, () => urlOwnerOf(this.cfg))
-    // Back / Forward re-apply the tab from the address and never write (writing would lose Forward).
+    // Back / Forward re-apply the tab from the address and never write (writing would lose Forward). Nested, this
+    // shell's tab is its own ?subtab= segment, never the owner's ?tab=.
     this._offAddress = onAddressChange(({ tab }) => {
-      const i = this.tabs.findIndex((t) => t.id === tab)
+      const id = urlOwnerOf(this.cfg) ? tab : this.nestedTab()
+      const i = this.tabs.findIndex((t) => t.id === id)
       this.select(i >= 0 ? i : 0, { fromHistory: true })
     })
     this.loadManifest()
@@ -268,10 +270,20 @@ export default defineComponent({
       let q = ''
       try { q = readViewKeys(location.search).tab } catch { /* non-browser */ }
       // On a page whose address this shell owns, the URL (a reload, a shared link) beats a baked cfg.tab, or the
-      // first-paint replace would overwrite the link with the default. Elsewhere the host's config leads.
-      const order = urlOwnerOf(this.cfg) ? [this.tab, q, this.cfg.tab] : [this.tab, this.cfg.tab, q]
+      // first-paint replace would overwrite the link with the default. Nested in another owner's page, this shell's
+      // tab is its ?subtab= segment (a deep link), and the host's config leads the rest.
+      const order = urlOwnerOf(this.cfg) ? [this.tab, q, this.cfg.tab] : [this.nestedTab(true), this.tab, this.cfg.tab, this.nestedTab()]
       return String(order.find((v) => v) || '').trim()
     },
+    // Nested (no owner here): this shell's segment of ?subtab=, else ?tab= when it names one of its own rows (a
+    // one-level partner page). Rows come from the full list, so a row that only arrives with the manifest still
+    // counts. An owner's own ?tab= (bundle__profile) never names one of them. segmentOnly: the segment alone.
+    nestedTab(segmentOnly = false) {
+      let seg = '', q = ''
+      try { seg = subtabAt(location.search, depthOf(this.cfg)); q = readViewKeys(location.search).tab } catch { /* non-browser */ }
+      if (seg || segmentOnly) return seg
+      return TABS.some((t) => t.id === q) ? q : ''
+    },
     initialIndex() {
       const i = this.tabs.findIndex((t) => t.id === this.requestedTab())
       return i >= 0 ? i : 0
@@ -344,8 +356,9 @@ export default defineComponent({
       return '../' + r
     },
     // The tab is written to the address by the ONE owner (urlOwner in profile-config: 'app' on our own pages,
-    // 'host' when a host's router writes, absent on a partner's page = read only). A reader's choice is a push;
-    // first paint is a replace; Back / Forward never write.
+    // 'host' when a host's router writes). Nested, it is announced, and the owner above records it as this shell's
+    // ?subtab= segment; on a partner's page nothing above listens. A reader's choice is a push; first paint is a
+    // replace, and nested it is REQUIRED, so the segment exists before a deeper one; Back / Forward never write.
     select(i, { fromHistory = false, firstPaint = false } = {}) {
       const prevIndex = this.activeIndex
       this.activeIndex = i
@@ -358,7 +371,7 @@ export default defineComponent({
       if (!t) return
       // Tell the host which plugin is showing (CustomEvent 'tab-change', detail[0] = { id, label }).
       if (prevIndex !== i || !this._announced) { this._announced = true; this.$emit('tab-change', { id: t.id, label: this.tabLabel(t) }) }
-      if (!fromHistory) writeViewKeys({ tab: t.id }, { owner: urlOwnerOf(this.cfg), push: !firstPaint, el: this.$el })
+      if (!fromHistory) claimView({ tab: t.id }, { owner: urlOwnerOf(this.cfg), push: !firstPaint, el: this.$el, depth: depthOf(this.cfg) })
       if (!t.scriptUrl) return   // applyManifest selects again once the manifest lands
       // A heavy tab's slot exists only after its v-if subtree renders, so mount on the next tick.
       if (!t.mounted) this.$nextTick(() => { if (this.activeIndex === i) this.mountElement(i) })
@@ -380,6 +393,8 @@ export default defineComponent({
       if (this.assetsBase) pc.assetsBase = this.assetsBase
       // The host owns its URL, hash and title: a nested plugin must not write them.
       pc.urlSync = false
+      // A shell nested in this tab claims the ?subtab= segment one below this shell's own.
+      pc.addressDepth = urlOwnerOf(this.cfg) ? 1 : depthOf(this.cfg) + 1
       // The plugin's own name for its print header: this tab's localized label.
       pc.mapTitle = this.tabLabel(t)
       return pc