diff --git a/apps/app/src/components-v2/layout/AppSidebar.vue b/apps/app/src/components-v2/layout/AppSidebar.vue
index 5607e1a3..03a7d061 100644
--- a/apps/app/src/components-v2/layout/AppSidebar.vue
+++ b/apps/app/src/components-v2/layout/AppSidebar.vue
@@ -32,6 +32,16 @@
  * is needed (two flex-1 siblings would split the column 50/50 and
  * compress the nav).
  *
+ * Plan 2.5 P6 Fix 9: explicit `h-screen` on the desktop <aside>. Without
+ * it the aside sized to its children's intrinsic heights (Header +
+ * SidebarNav-at-min-content + WorkspaceSwitcher ≈ 250-400px) and ended
+ * mid-viewport, even though the surrounding grid row stretched to 100vh.
+ * With `h-screen` the aside fills the viewport vertically, the
+ * SidebarNav `flex-1` expands to claim the remaining column space, and
+ * WorkspaceSwitcher anchors to the true bottom — matching crewli-starter.
+ * The mobile Drawer doesn't need this — PrimeVue Drawer sizes its content
+ * container to 100% of the panel height via internal pt classes.
+ *
  * Deliberate simplification: crewli-starter's bespoke Teleport tooltip (shown in
  * collapsed mode for nav items) is NOT ported here. SidebarNav already provides
  * native `:title` tooltips in collapsed mode, which is functionally equivalent
@@ -81,7 +91,7 @@ const mobileVisible = computed<boolean>({
   -->
   <!-- desktop -->
   <aside
-    class="hidden lg:flex flex-col overflow-hidden bg-[var(--p-surface-card)] border-e border-[var(--p-content-border-color)] z-40 transition-[width] duration-200 flex-shrink-0"
+    class="hidden lg:flex h-screen sticky top-0 flex-col overflow-hidden bg-[var(--p-surface-card)] border-e border-[var(--p-content-border-color)] z-40 transition-[width] duration-200 flex-shrink-0"
     :class="shell.sidebarCollapsed ? 'w-16' : 'w-64'"
   >
     <SidebarHeader />
diff --git a/apps/app/src/components-v2/layout/AppTopbar.vue b/apps/app/src/components-v2/layout/AppTopbar.vue
index ecceffc9..16f84803 100644
--- a/apps/app/src/components-v2/layout/AppTopbar.vue
+++ b/apps/app/src/components-v2/layout/AppTopbar.vue
@@ -97,12 +97,14 @@ const mobileOrgInitials = computed<string>(() => {
 })
 
 // ---------------------------------------------------------------------------
-// Density toggle
+// Density toggle (Plan 2.5 P6 Fix 10)
 // ---------------------------------------------------------------------------
-
-function toggleDensity(): void {
-  shell.setDensity(shell.density === 'comfortable' ? 'compact' : 'comfortable')
-}
+//
+// Wiring delegates to shell.toggleDensity() (the binary comfortable ⇔ compact
+// flip lives in the store so applyDomAttributes() fires synchronously).
+// Icon and aria-label follow the dark-toggle convention: they describe the
+// TARGET state — when current density is comfortable, the button promises
+// to switch to compact and shows the small-density icon.
 
 const densityAriaLabel = computed<string>(() =>
   shell.density === 'comfortable' ? 'Switch to compact' : 'Switch to comfortable',
@@ -110,8 +112,8 @@ const densityAriaLabel = computed<string>(() =>
 
 const densityIcon = computed<string>(() =>
   shell.density === 'comfortable'
-    ? 'tabler-layout-distribute-vertical'
-    : 'tabler-layout-distribute-horizontal',
+    ? 'tabler-baseline-density-small'
+    : 'tabler-baseline-density-medium',
 )
 
 // ---------------------------------------------------------------------------
@@ -314,9 +316,11 @@ const userMenuItems = computed<MenuItem[]>(() => [
       -->
       <button
         type="button"
+        data-testid="density-toggle"
         class="inline-flex h-[38px] w-[38px] items-center justify-center rounded-[var(--p-border-radius)] border-0 bg-transparent text-[var(--p-text-muted-color)] transition-colors duration-150 hover:bg-[var(--p-content-hover-background)] hover:text-[var(--p-text-color)] focus-visible:outline focus-visible:outline-2 focus-visible:outline-[var(--p-primary-color)] focus-visible:outline-offset-1"
         :aria-label="densityAriaLabel"
-        @click="toggleDensity"
+        :title="densityAriaLabel"
+        @click="shell.toggleDensity()"
       >
         <Icon
           :name="densityIcon"
diff --git a/apps/app/src/components-v2/layout/__tests__/AppTopbar.spec.ts b/apps/app/src/components-v2/layout/__tests__/AppTopbar.spec.ts
index bef4a510..08dd0cb9 100644
--- a/apps/app/src/components-v2/layout/__tests__/AppTopbar.spec.ts
+++ b/apps/app/src/components-v2/layout/__tests__/AppTopbar.spec.ts
@@ -161,13 +161,18 @@ describe('AppTopbar', () => {
   // Density toggle → setDensity with flipped value
   // -------------------------------------------------------------------------
 
-  it('density toggle flips comfortable → compact', async () => {
+  // Plan 2.5 P6 Fix 10: the density button now delegates to the
+  // store's toggleDensity action (binary flip + applyDomAttributes
+  // in one place). aria-label still reflects the target state so
+  // these specs assert on the user-facing label.
+
+  it('density toggle (comfortable state) calls shell.toggleDensity()', async () => {
     const wrapper = mountTopbar()
     const shell = useShellUiStore()
 
     shell.density = 'comfortable'
 
-    const spy = vi.spyOn(shell, 'setDensity')
+    const spy = vi.spyOn(shell, 'toggleDensity')
 
     const densityBtn = wrapper.find('button[aria-label="Switch to compact"]')
 
@@ -175,16 +180,16 @@ describe('AppTopbar', () => {
 
     await densityBtn.trigger('click')
 
-    expect(spy).toHaveBeenCalledWith('compact')
+    expect(spy).toHaveBeenCalledOnce()
   })
 
-  it('density toggle flips compact → comfortable', async () => {
+  it('density toggle (compact state) calls shell.toggleDensity()', async () => {
     const wrapper = mountTopbar()
     const shell = useShellUiStore()
 
     shell.density = 'compact'
 
-    const spy = vi.spyOn(shell, 'setDensity')
+    const spy = vi.spyOn(shell, 'toggleDensity')
 
     await wrapper.vm.$nextTick()
 
@@ -194,7 +199,41 @@ describe('AppTopbar', () => {
 
     await densityBtn.trigger('click')
 
-    expect(spy).toHaveBeenCalledWith('comfortable')
+    expect(spy).toHaveBeenCalledOnce()
+  })
+
+  // Fix 10 (Plan 2.5 P6) regression locks: density button is reachable
+  // by stable test selector, and the topbar right-side action order
+  // matches the crewli-starter reference (search → density → dark →
+  // notifications → user). Implementation reorders should not regress.
+
+  it('density toggle is reachable by data-testid="density-toggle"', () => {
+    const wrapper = mountTopbar()
+
+    expect(wrapper.find('[data-testid="density-toggle"]').exists()).toBe(true)
+  })
+
+  it('topbar right-side actions render in order: search → density → dark → notifications → user', () => {
+    const wrapper = mountTopbar()
+    const bar = wrapper.findComponent(MenubarStub)
+    const html = bar.html()
+
+    const idxSearch = html.indexOf('data-tb="search"')
+    const idxDensity = html.indexOf('data-testid="density-toggle"')
+    const idxDark = html.indexOf('aria-label="Switch to dark mode"')
+    const idxNotif = html.indexOf('data-tb="notifications"')
+    const idxUser = html.indexOf('data-tb="user"')
+
+    expect(idxSearch).toBeGreaterThanOrEqual(0)
+    expect(idxDensity).toBeGreaterThanOrEqual(0)
+    expect(idxDark).toBeGreaterThanOrEqual(0)
+    expect(idxNotif).toBeGreaterThanOrEqual(0)
+    expect(idxUser).toBeGreaterThanOrEqual(0)
+
+    expect(idxSearch).toBeLessThan(idxDensity)
+    expect(idxDensity).toBeLessThan(idxDark)
+    expect(idxDark).toBeLessThan(idxNotif)
+    expect(idxNotif).toBeLessThan(idxUser)
   })
 
   // -------------------------------------------------------------------------
diff --git a/apps/app/src/stores/__tests__/useShellUiStore.spec.ts b/apps/app/src/stores/__tests__/useShellUiStore.spec.ts
index bd53b6f8..928bd393 100644
--- a/apps/app/src/stores/__tests__/useShellUiStore.spec.ts
+++ b/apps/app/src/stores/__tests__/useShellUiStore.spec.ts
@@ -57,6 +57,33 @@ describe('useShellUiStore', () => {
     s.setMobileOpen(false)
     expect(s.mobileOpen).toBe(false)
   })
+
+  // Plan 2.5 P6 Fix 10 — toggleDensity is the binary UI flip exposed by
+  // the topbar density button. Calls applyDomAttributes() so the
+  // <html data-density> attribute mutates synchronously (consumers
+  // like the AppShellV2 watcher would also fire, but the synchronous
+  // contract is what topbar callers rely on).
+  it('toggleDensity flips comfortable ⇔ compact and writes data-density', () => {
+    const s = useShellUiStore()
+
+    expect(s.density).toBe('comfortable')
+    s.toggleDensity()
+    expect(s.density).toBe('compact')
+    expect(document.documentElement.getAttribute('data-density')).toBe('compact')
+    s.toggleDensity()
+    expect(s.density).toBe('comfortable')
+    expect(document.documentElement.getAttribute('data-density')).toBe('comfortable')
+  })
+
+  it('toggleDensity from compact returns to comfortable on the second call', () => {
+    const s = useShellUiStore()
+
+    s.setDensity('compact')
+    s.toggleDensity()
+    expect(s.density).toBe('comfortable')
+    s.toggleDensity()
+    expect(s.density).toBe('compact')
+  })
 })
 
 describe('applyDomAttributes — dark mode (AD-2.5-D1)', () => {
diff --git a/apps/app/src/stores/useShellUiStore.ts b/apps/app/src/stores/useShellUiStore.ts
index a4d5c0fd..369e1f3b 100644
--- a/apps/app/src/stores/useShellUiStore.ts
+++ b/apps/app/src/stores/useShellUiStore.ts
@@ -44,6 +44,18 @@ export const useShellUiStore = defineStore('shellUi', () => {
     density.value = next
   }
 
+  /**
+   * Plan 2.5 P6 Fix 10: binary UI toggle between the two density extremes
+   * the topbar exposes. Calls applyDomAttributes() so consumers (PrimeVue
+   * Aura preset + Tailwind component styles) react to the new
+   * <html data-density> immediately, mirroring how AppShellV2's watcher
+   * would update on a setDensity() call but synchronously.
+   */
+  function toggleDensity(): void {
+    density.value = density.value === 'compact' ? 'comfortable' : 'compact'
+    applyDomAttributes()
+  }
+
   function applyDomAttributes(): void {
     const el = document.documentElement
 
@@ -79,6 +91,7 @@ export const useShellUiStore = defineStore('shellUi', () => {
     setMobileOpen,
     setTheme,
     setDensity,
+    toggleDensity,
     applyDomAttributes,
     openDrawer,
     closeDrawer,