diff --git a/extension/src/popup/components/__tests__/org-switcher.test.ts b/extension/src/popup/components/__tests__/org-switcher.test.ts
index b64205d..d4fd1d1 100644
--- a/extension/src/popup/components/__tests__/org-switcher.test.ts
+++ b/extension/src/popup/components/__tests__/org-switcher.test.ts
@@ -40,8 +40,9 @@ describe('popup/org-switcher', () => {
     const sel = host.querySelector('select') as HTMLSelectElement;
     sel.value = 'org-1';
     sel.dispatchEvent(new Event('change'));
-    // Two awaits: one for org_switch, one for the subsequent list load.
-    // navigate('list') fires after both resolve.
+    // Three awaits: org_switch, list load, then org_list_collections fetch.
+    // navigate('list') fires after all three resolve.
+    await Promise.resolve();
     await Promise.resolve();
     await Promise.resolve();
 
diff --git a/extension/src/popup/components/org-switcher.ts b/extension/src/popup/components/org-switcher.ts
index 6d71a21..a2e5a0c 100644
--- a/extension/src/popup/components/org-switcher.ts
+++ b/extension/src/popup/components/org-switcher.ts
@@ -6,7 +6,7 @@
 // org renders a read-only banner; Dev-C's write UI reads `orgOffline` to
 // disable writes.
 
-import type { OrgConfigSummary, OrgManifestEntry, ManifestEntry, ItemId } from '../../shared/types';
+import type { OrgConfigSummary, OrgManifestEntry, ManifestEntry, ItemId, Collection } from '../../shared/types';
 import { sendMessage, setState, navigate, getState } from '../../shared/state';
 import { messageForList, normalizeOrgEntries } from '../../shared/org-context';
 
@@ -73,6 +73,16 @@ export async function renderOrgSwitcher(host: HTMLElement): Promise<void> {
       setState({ entries });
     }
 
+    // Fetch (or clear) the collection list for the new context. Any existing
+    // collection filter is also cleared on personal switch so the next org
+    // switch starts with no stale filter.
+    if (data.context === 'personal') {
+      setState({ orgCollections: [], collectionFilter: undefined });
+    } else {
+      const colResp = await sendMessage({ type: 'org_list_collections' });
+      if (colResp.ok) setState({ orgCollections: colResp.data as Collection[] });
+    }
+
     navigate('list', {});
   };
 
diff --git a/extension/src/shared/popup-state.ts b/extension/src/shared/popup-state.ts
index 777d2bc..3b384db 100644
--- a/extension/src/shared/popup-state.ts
+++ b/extension/src/shared/popup-state.ts
@@ -57,6 +57,7 @@ export interface PopupState {
   orgOffline?: boolean;
   orgConfigs?: OrgConfigSummary[];
   orgCollections?: Collection[];
+  collectionFilter?: string;
   // Vault-tab-only fields. The popup surface leaves these at their defaults
   // (unlocked=false implicit via separate lock-screen view, drawer/panel false).
   // Kept on the shared shape so VaultState satisfies StateHost.getState()
diff --git a/extension/src/vault/__tests__/collection-facet.test.ts b/extension/src/vault/__tests__/collection-facet.test.ts
index 9702df8..2c0a235 100644
--- a/extension/src/vault/__tests__/collection-facet.test.ts
+++ b/extension/src/vault/__tests__/collection-facet.test.ts
@@ -15,9 +15,10 @@ vi.mock('../../shared/state', () => ({
 }));
 
 import { renderCollectionFacet } from '../vault-sidebar';
-import { getState } from '../../shared/state';
+import { getState, setState } from '../../shared/state';
 
 const mockGetState = getState as ReturnType<typeof vi.fn>;
+const mockSetState = setState as ReturnType<typeof vi.fn>;
 
 describe('vault collection facet (org context)', () => {
   beforeEach(() => {
@@ -38,4 +39,31 @@ describe('vault collection facet (org context)', () => {
 
     expect(el.textContent).toContain('Production Infra');
   });
+
+  it('clicking a collection row calls setState with the collection filter', () => {
+    mockGetState.mockReturnValue({
+      orgContext: 'org-1',
+      orgCollections: [{ slug: 'prod-infra', display_name: 'Production Infra' }],
+      collectionFilter: undefined,
+    });
+    const el = document.getElementById('facet')!;
+    renderCollectionFacet(el);
+
+    const btn = el.querySelector<HTMLButtonElement>('[data-slug="prod-infra"]')!;
+    expect(btn).not.toBeNull();
+    btn.click();
+
+    expect(mockSetState).toHaveBeenCalledWith({ collectionFilter: 'prod-infra' });
+  });
+
+  it('renders nothing in personal context', () => {
+    mockGetState.mockReturnValue({
+      orgContext: 'personal',
+      orgCollections: [],
+    });
+    const el = document.getElementById('facet')!;
+    renderCollectionFacet(el);
+
+    expect(el.innerHTML).toBe('');
+  });
 });
diff --git a/extension/src/vault/vault-context.ts b/extension/src/vault/vault-context.ts
index 8d38d0a..b84004b 100644
--- a/extension/src/vault/vault-context.ts
+++ b/extension/src/vault/vault-context.ts
@@ -41,6 +41,7 @@ export interface VaultState {
   capturedTabId: number | null;
   capturedUrl: string;
   historyItemId: ItemId | null;
+  collectionFilter?: string;
 }
 
 // The controller passed to every vault-* module. vault.ts builds one instance
@@ -117,6 +118,11 @@ export function getFilteredEntries(
       return false;
     });
   }
+  if (state.collectionFilter) {
+    filtered = filtered.filter(
+      ([, e]) => (e as { collection?: string }).collection === state.collectionFilter,
+    );
+  }
   filtered.sort((a, b) => a[1].title.localeCompare(b[1].title));
   return filtered;
 }
diff --git a/extension/src/vault/vault-sidebar.ts b/extension/src/vault/vault-sidebar.ts
index 5158997..11e51d3 100644
--- a/extension/src/vault/vault-sidebar.ts
+++ b/extension/src/vault/vault-sidebar.ts
@@ -11,9 +11,9 @@ import {
 } from '../shared/glyphs';
 import { renderStatusIndicator, type VaultStatus } from './vault-status';
 import {
-  type VaultController, typeIcon, typeLabel, getFilteredEntries,
+  type VaultController, typeIcon, typeLabel, getFilteredEntries, escapeHtml,
 } from './vault-context';
-import { getState } from '../shared/state';
+import { getState, setState } from '../shared/state';
 
 const SEARCH_DEBOUNCE_MS = 80;
 
@@ -33,6 +33,7 @@ export function renderSidebarShell(): string {
             <input type="text" id="vault-search" placeholder="/ search…" />
           </div>
           <nav class="vault-sidebar__categories" id="vault-categories" aria-label="Item types"></nav>
+          <nav class="vault-sidebar__collections" id="vault-collections" aria-label="Collections"></nav>
           <div class="vault-sidebar__nav">
             <button class="vault-sidebar__nav-item vault-sidebar__nav-item--primary" data-nav="add" title="New item">+ new item</button>
             <button class="vault-sidebar__nav-item" data-nav="trash" title="Trash">${GLYPH_TRASH} <span class="vault-sidebar__nav-label">trash</span></button>
@@ -189,6 +190,14 @@ export function renderSidebarCategories(ctx: VaultController): void {
       ctx.closeDrawer();
     });
   });
+
+  // Keep the collection facet in sync — it must (re)render whenever
+  // orgCollections / orgContext / collectionFilter change, and
+  // renderSidebarCategories is already the re-render hook that runs after
+  // each of those state mutations (via the vault host's setState → renderPane
+  // → render → renderShell → ctx.renderSidebarCategories chain).
+  const collSlot = document.getElementById('vault-collections');
+  if (collSlot) renderCollectionFacet(collSlot, ctx);
 }
 
 // ---------------------------------------------------------------------------
@@ -197,18 +206,52 @@ export function renderSidebarCategories(ctx: VaultController): void {
 
 /// Render a collection nav (parallel to the type-category nav) into `host`,
 /// shown only in org context. Selecting a collection filters the org list to
-/// that slug.
+/// that slug. Hidden (host cleared) in personal context.
 ///
-/// SCAFFOLD STATE (HOLD until Dev-A merges): renders the empty container only.
-/// Populating from getState().orgCollections, the click-to-filter wiring, and
-/// the org_list_collections fetch on org_switch are held until Dev-A's org
-/// messages land.
-export function renderCollectionFacet(host: HTMLElement): void {
-  // Inline shape until orgCollections joins PopupState at integration (it needs
-  // Dev-A's Collection type). HOLD(dev-a): render each as a vault-category-row
-  // mirroring renderSidebarCategories, wired to set a collection filter.
-  const collections =
-    (getState() as { orgCollections?: Array<{ slug: string; display_name: string }> }).orgCollections ?? [];
-  host.innerHTML =
-    `<nav class="vault-sidebar__collections" aria-label="Collections" data-count="${collections.length}"></nav>`;
+/// `ctx` is provided when called from renderSidebarCategories (production); it
+/// is absent in tests that mount the facet in isolation via happy-dom.
+export function renderCollectionFacet(host: HTMLElement, ctx?: VaultController): void {
+  const s = getState();
+  const orgContext = s.orgContext;
+  const orgCollections = s.orgCollections ?? [];
+  const collectionFilter = s.collectionFilter;
+
+  if (!orgContext || orgContext === 'personal') {
+    host.innerHTML = '';
+    return;
+  }
+
+  const isAllActive = !collectionFilter;
+  let html = `
+    <button class="vault-category-row ${isAllActive ? 'vault-category-row--active' : ''}" data-slug="">
+      <span class="vault-category-row__icon">⊞</span>
+      <span class="vault-category-row__label vault-sidebar__category-label">All collections</span>
+    </button>`;
+
+  for (const col of orgCollections) {
+    const isActive = collectionFilter === col.slug;
+    html += `
+    <button class="vault-category-row ${isActive ? 'vault-category-row--active' : ''}" data-slug="${escapeHtml(col.slug)}">
+      <span class="vault-category-row__icon">◈</span>
+      <span class="vault-category-row__label vault-sidebar__category-label">${escapeHtml(col.display_name)}</span>
+    </button>`;
+  }
+
+  host.innerHTML = html;
+
+  host.querySelectorAll<HTMLButtonElement>('.vault-category-row').forEach((btn) => {
+    btn.addEventListener('click', () => {
+      const slug = btn.dataset.slug || undefined;
+      setState({ collectionFilter: slug });
+      if (ctx) {
+        // Re-render categories (updates type counts for the new filter) which
+        // in turn re-renders the facet to update the active highlight.
+        renderSidebarCategories(ctx);
+        ctx.renderListPane();
+      } else {
+        // Test path (no ctx): just re-render the facet for the highlight update.
+        renderCollectionFacet(host, ctx);
+      }
+    });
+  });
 }