diff --git a/src/actions/ai-import.ts b/src/actions/ai-import.ts
index ea30d5c..c276886 100644
--- a/src/actions/ai-import.ts
+++ b/src/actions/ai-import.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { assertBrandAccess } from "@/lib/brand-scope";
 import { parseExcelBuffer, parseTextBuffer } from "@/lib/excel-parser";
 import { importProductsBatch } from "@/actions/import-products";
 import { importOrdersBatch } from "@/actions/import-orders";
@@ -41,7 +42,9 @@ export async function analyzeImport(
 ): Promise<AnalyzeImportResult> {
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Not authenticated" };
-  if (adminUser.role === "brand_admin" && adminUser.brand_id !== brandId) {
+  try {
+    assertBrandAccess(adminUser, brandId);
+  } catch {
     return { success: false, error: "Not authorized for this brand" };
   }
 
diff --git a/src/actions/analytics.ts b/src/actions/analytics.ts
index b656b07..1fd2dd2 100644
--- a/src/actions/analytics.ts
+++ b/src/actions/analytics.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -96,7 +97,7 @@ async function brandScopedRPC<T>(
   const adminUser = await getAdminUser();
   if (!adminUser) throw new Error("Not authenticated");
 
-  const brandId = adminUser.brand_id ?? null;
+  const brandId = await getActiveBrandId(adminUser);
 
   const response = await fetch(`${supabaseUrl}/rest/v1/rpc/${rpcName}`, {
     method: "POST",
@@ -232,7 +233,7 @@ export async function getRecentOrders(limit: number = 10): Promise<RecentOrder[]
     const adminUser = await getAdminUser();
     if (!adminUser) throw new Error("Not authenticated");
 
-    const brandId = adminUser.brand_id ?? null;
+    const brandId = await getActiveBrandId(adminUser);
 
     const params = new URLSearchParams({
       select: "id,customer_name,subtotal,status,created_at,fulfillment",
@@ -293,7 +294,7 @@ export async function getConversionFunnel(): Promise<ConversionFunnel[]> {
     const adminUser = await getAdminUser();
     if (!adminUser) throw new Error("Not authenticated");
 
-    const brandId = adminUser.brand_id ?? null;
+    const brandId = await getActiveBrandId(adminUser);
 
     const params = new URLSearchParams({
       select: "id,status",
diff --git a/src/actions/brands.ts b/src/actions/brands.ts
new file mode 100644
index 0000000..fdd5866
--- /dev/null
+++ b/src/actions/brands.ts
@@ -0,0 +1,65 @@
+import "server-only";
+
+import { getAdminUser } from "@/lib/admin-permissions";
+import { svcHeaders } from "@/lib/svc-headers";
+
+export type BrandListItem = {
+  id: string;
+  name: string;
+  slug: string;
+  logo_url: string | null;
+};
+
+/**
+ * Returns the list of brands the current admin user can act in.
+ *
+ * - platform_admin: all brands (queried directly from the `brands` table)
+ * - everyone else: brands in `adminUser.brand_ids`
+ * - empty array for unauthenticated / no-access admins
+ *
+ * This is a plain async function (not a server action) so it can be called
+ * from server components and server actions without the "use server" wrapper.
+ * The BrandSelector client component receives the result as a prop.
+ */
+export async function listBrandsForAdmin(): Promise<BrandListItem[]> {
+  const adminUser = await getAdminUser();
+  if (!adminUser) return [];
+
+  const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL;
+  const serviceKey = process.env.SUPABASE_SERVICE_ROLE_KEY;
+  if (!supabaseUrl || !serviceKey) return [];
+
+  if (adminUser.role === "platform_admin") {
+    try {
+      const res = await fetch(
+        `${supabaseUrl}/rest/v1/brands?select=id,name,slug,logo_url&order=name`,
+        { headers: svcHeaders(serviceKey), cache: "no-store" }
+      );
+      if (!res.ok) return [];
+      const data = await res.json();
+      return Array.isArray(data) ? data : [];
+    } catch {
+      return [];
+    }
+  }
+
+  if (adminUser.brand_ids.length === 0) return [];
+
+  // Use PostgREST `in` filter. The brand_ids are UUIDs, so the quoting
+  // pattern in the spec is safe; the inner quotes are required by PostgREST
+  // for UUID literals.
+  const filter = `id=in.(${adminUser.brand_ids
+    .map((id) => `"${id}"`)
+    .join(",")})`;
+  try {
+    const res = await fetch(
+      `${supabaseUrl}/rest/v1/brands?${filter}&select=id,name,slug,logo_url&order=name`,
+      { headers: svcHeaders(serviceKey), cache: "no-store" }
+    );
+    if (!res.ok) return [];
+    const data = await res.json();
+    return Array.isArray(data) ? data : [];
+  } catch {
+    return [];
+  }
+}
diff --git a/src/actions/communications/campaigns.ts b/src/actions/communications/campaigns.ts
index d752956..2a5c64d 100644
--- a/src/actions/communications/campaigns.ts
+++ b/src/actions/communications/campaigns.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 export type CampaignType = "marketing" | "operational" | "transactional";
@@ -57,7 +58,11 @@ export async function getCommunicationCampaigns(brandId?: string): Promise<ListC
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Not authenticated" };
 
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? null;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  const effectiveBrandId = activeBrandId;
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
   const supabaseKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!;
@@ -147,7 +152,7 @@ export async function deleteCampaign(campaignId: string, brandId?: string): Prom
     {
       method: "POST",
       headers: { ...svcHeaders(supabaseKey), "Content-Type": "application/json" },
-      body: JSON.stringify({ p_campaign_id: campaignId, p_brand_id: adminUser.brand_id ?? null }),
+      body: JSON.stringify({ p_campaign_id: campaignId, p_brand_id: (await getActiveBrandId(adminUser)) ?? null }),
     }
   );
 
@@ -167,7 +172,7 @@ export async function getCampaignById(campaignId: string, brandId?: string): Pro
     {
       method: "POST",
       headers: { ...svcHeaders(supabaseKey), "Content-Type": "application/json" },
-      body: JSON.stringify({ p_campaign_id: campaignId, p_brand_id: brandId ?? adminUser.brand_id ?? null }),
+      body: JSON.stringify({ p_campaign_id: campaignId, p_brand_id: (await getActiveBrandId(adminUser, brandId)) ?? null }),
     }
   );
 
diff --git a/src/actions/communications/send.ts b/src/actions/communications/send.ts
index 9fe1c48..ce97ec9 100644
--- a/src/actions/communications/send.ts
+++ b/src/actions/communications/send.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 import type { AudienceRules } from "./campaigns";
 
@@ -120,11 +121,15 @@ export async function sendCampaign(campaignId: string, brandId?: string): Promis
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Not authenticated" };
 
-  // Resolve brand from campaign or parameter
-  const effectiveBrandId = brandId ?? adminUser.brand_id;
+  // Resolve brand from campaign or parameter (URL > cookie > legacy > first of brand_ids)
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  const effectiveBrandId = activeBrandId;
 
   // Brand scoping: brand_admin can only send their own brand's campaigns
-  if (adminUser.role === "brand_admin" && effectiveBrandId && adminUser.brand_id !== effectiveBrandId) {
+  if (adminUser.role === "brand_admin" && effectiveBrandId && !adminUser.brand_ids.includes(effectiveBrandId)) {
     return { success: false, error: "Not authorized to send this brand's campaigns" };
   }
 
diff --git a/src/actions/communications/templates.ts b/src/actions/communications/templates.ts
index 0ee0651..98907fa 100644
--- a/src/actions/communications/templates.ts
+++ b/src/actions/communications/templates.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 import type { AudienceRules } from "./campaigns";
 
@@ -33,7 +34,11 @@ export async function getCommunicationTemplates(brandId?: string): Promise<{ suc
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Not authenticated" };
 
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? null;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  const effectiveBrandId = activeBrandId;
 
   // Brand scoping: brand_admin can only see their own brand's templates
   if (adminUser.role === "brand_admin" && effectiveBrandId && effectiveBrandId !== adminUser.brand_id) {
@@ -112,7 +117,7 @@ export async function getTemplateById(templateId: string): Promise<Template | nu
     {
       method: "POST",
       headers: { ...svcHeaders(supabaseKey), "Content-Type": "application/json" },
-      body: JSON.stringify({ p_brand_id: adminUser.brand_id ?? null }),
+      body: JSON.stringify({ p_brand_id: (await getActiveBrandId(adminUser)) ?? null }),
     }
   );
 
diff --git a/src/actions/dashboard.ts b/src/actions/dashboard.ts
index fb11dd7..e5c2b0d 100644
--- a/src/actions/dashboard.ts
+++ b/src/actions/dashboard.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -66,7 +67,7 @@ export async function getDashboardStats(): Promise<DashboardStats> {
     const adminUser = await getAdminUser();
     if (!adminUser) throw new Error("Not authenticated");
 
-    const brandId = adminUser.brand_id ?? null;
+    const brandId = await getActiveBrandId(adminUser);
 
     // Get today's date range
     const today = new Date();
@@ -202,7 +203,7 @@ export async function getDashboardSummary(): Promise<DashboardSummary> {
     const adminUser = await getAdminUser();
     if (!adminUser) throw new Error("Not authenticated");
 
-    const brandId = adminUser.brand_id ?? null;
+    const brandId = await getActiveBrandId(adminUser);
     const thirtyDaysAgo = new Date();
     thirtyDaysAgo.setDate(thirtyDaysAgo.getDate() - 30);
 
diff --git a/src/actions/locations.ts b/src/actions/locations.ts
index ec3dc92..b2b1d1a 100644
--- a/src/actions/locations.ts
+++ b/src/actions/locations.ts
@@ -2,6 +2,7 @@
 
 import { revalidateTag } from "next/cache";
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 export type LocationInput = {
@@ -48,7 +49,11 @@ export async function createLocation(
   if (!adminUser.can_manage_stops) {
     return { success: false, error: "Not authorized to manage locations" };
   }
-  const effectiveBrandId = brandId || adminUser.brand_id;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  const effectiveBrandId = activeBrandId;
   if (!effectiveBrandId) return { success: false, error: "No brand selected" };
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -96,7 +101,11 @@ export async function createLocationsBatch(
   if (!adminUser.can_manage_stops) {
     return { success: false, created: 0, error: "Not authorized" };
   }
-  const effectiveBrandId = brandId || adminUser.brand_id;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, created: 0, error: "Brand access required" };
+  }
+  const effectiveBrandId = activeBrandId;
   if (!effectiveBrandId) return { success: false, created: 0, error: "No brand selected" };
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -206,7 +215,8 @@ export async function adminListLocations(
 
   // Application-layer brand scoping: platform_admin (brand_id: null) gets all
   // brands; everyone else gets only their own brand.
-  const effectiveBrandId = brandId || adminUser.brand_id;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  const effectiveBrandId = activeBrandId;
 
   const res = await fetch(
     `${supabaseUrl}/rest/v1/rpc/admin_list_locations`,
diff --git a/src/actions/orders/create-admin-order.ts b/src/actions/orders/create-admin-order.ts
index 03a4156..493451d 100644
--- a/src/actions/orders/create-admin-order.ts
+++ b/src/actions/orders/create-admin-order.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 import { randomUUID } from "crypto";
 
@@ -41,7 +42,11 @@ export async function createAdminOrder(
   }
 
   // Brand scoping
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? null;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  const effectiveBrandId = activeBrandId;
   if (adminUser.role === "brand_admin" && adminUser.brand_id && effectiveBrandId !== adminUser.brand_id) {
     return { success: false, error: "Not authorized for this brand" };
   }
diff --git a/src/actions/payments.ts b/src/actions/payments.ts
index c182359..d9a624c 100644
--- a/src/actions/payments.ts
+++ b/src/actions/payments.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { assertBrandAccess } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 export type PaymentProvider = "stripe" | "square" | "manual";
@@ -65,10 +66,9 @@ export async function savePaymentSettings(params: {
     return { success: false, error: "Not authorized" };
   }
 
-  if (
-    adminUser.role === "brand_admin" &&
-    adminUser.brand_id !== params.brandId
-  ) {
+  try {
+    assertBrandAccess(adminUser, params.brandId);
+  } catch {
     return { success: false, error: "Not authorized for this brand" };
   }
 
diff --git a/src/actions/products.ts b/src/actions/products.ts
index 9d5c947..0a91005 100644
--- a/src/actions/products.ts
+++ b/src/actions/products.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 export async function deleteProduct(
@@ -16,7 +17,11 @@ export async function deleteProduct(
     return { success: false, error: "Not authorized to manage products" };
   }
 
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? null;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  const effectiveBrandId = activeBrandId;
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
   const supabaseKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!;
diff --git a/src/actions/route-trace/lots.ts b/src/actions/route-trace/lots.ts
index 5d9b19d..bf81738 100644
--- a/src/actions/route-trace/lots.ts
+++ b/src/actions/route-trace/lots.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId, assertBrandAccess } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 const SUPABASE_URL = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -153,7 +154,14 @@ export interface FieldYieldSummary {
 export async function getRouteTraceLots(brandId: string, status?: string) {
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Unauthorized" };
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? undefined;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  if (activeBrandId) {
+    try { assertBrandAccess(adminUser, activeBrandId); } catch { return { success: false, error: "Brand access denied" }; }
+  }
+  const effectiveBrandId = activeBrandId ?? undefined;
   if (!effectiveBrandId) return { success: false, error: "No brand" };
 
   try {
@@ -235,7 +243,14 @@ export async function createHarvestLot(
 ) {
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Unauthorized" };
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? undefined;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  if (activeBrandId) {
+    try { assertBrandAccess(adminUser, activeBrandId); } catch { return { success: false, error: "Brand access denied" }; }
+  }
+  const effectiveBrandId = activeBrandId ?? undefined;
   if (!effectiveBrandId) return { success: false, error: "No brand" };
 
   try {
@@ -298,7 +313,14 @@ export async function updateHarvestLotStatus(
 export async function getRouteTraceStats(brandId: string) {
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Unauthorized" };
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? undefined;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  if (activeBrandId) {
+    try { assertBrandAccess(adminUser, activeBrandId); } catch { return { success: false, error: "Brand access denied" }; }
+  }
+  const effectiveBrandId = activeBrandId ?? undefined;
   if (!effectiveBrandId) return { success: false, error: "No brand" };
 
   try {
@@ -318,7 +340,14 @@ export async function getRouteTraceStats(brandId: string) {
 export async function searchHarvestLots(brandId: string, query: string) {
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Unauthorized" };
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? undefined;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  if (activeBrandId) {
+    try { assertBrandAccess(adminUser, activeBrandId); } catch { return { success: false, error: "Brand access denied" }; }
+  }
+  const effectiveBrandId = activeBrandId ?? undefined;
   if (!effectiveBrandId) return { success: false, error: "No brand" };
 
   try {
@@ -347,7 +376,14 @@ export async function getTraceChain(lotId: string) {
 export async function getHarvestLotsReadyToHaul(brandId: string) {
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Unauthorized" };
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? undefined;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  if (activeBrandId) {
+    try { assertBrandAccess(adminUser, activeBrandId); } catch { return { success: false, error: "Brand access denied" }; }
+  }
+  const effectiveBrandId = activeBrandId ?? undefined;
   if (!effectiveBrandId) return { success: false, error: "No brand" };
 
   try {
@@ -364,7 +400,14 @@ export async function getHarvestLotsReadyToHaul(brandId: string) {
 export async function getFieldYieldSummary(brandId: string) {
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Unauthorized" };
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? undefined;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  if (activeBrandId) {
+    try { assertBrandAccess(adminUser, activeBrandId); } catch { return { success: false, error: "Brand access denied" }; }
+  }
+  const effectiveBrandId = activeBrandId ?? undefined;
   if (!effectiveBrandId) return { success: false, error: "No brand" };
 
   try {
@@ -405,7 +448,14 @@ export interface InventoryByCrop {
 export async function getInventoryByCrop(brandId: string): Promise<{ success: true; inventory: InventoryByCrop[] } | { success: false; error: string }> {
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Unauthorized" };
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? undefined;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  if (activeBrandId) {
+    try { assertBrandAccess(adminUser, activeBrandId); } catch { return { success: false, error: "Brand access denied" }; }
+  }
+  const effectiveBrandId = activeBrandId ?? undefined;
   if (!effectiveBrandId) return { success: false, error: "No brand" };
 
   try {
@@ -451,7 +501,14 @@ export async function getRecentLotEvents(
 ): Promise<{ success: true; events: RecentLotEvent[] } | { success: false; error: string }> {
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Unauthorized" };
-  const effectiveBrandId = brandId ?? adminUser.brand_id ?? undefined;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, error: "Brand access required" };
+  }
+  if (activeBrandId) {
+    try { assertBrandAccess(adminUser, activeBrandId); } catch { return { success: false, error: "Brand access denied" }; }
+  }
+  const effectiveBrandId = activeBrandId ?? undefined;
   if (!effectiveBrandId) return { success: false, error: "No brand" };
 
   try {
diff --git a/src/actions/set-active-brand.ts b/src/actions/set-active-brand.ts
new file mode 100644
index 0000000..739f1a5
--- /dev/null
+++ b/src/actions/set-active-brand.ts
@@ -0,0 +1,47 @@
+"use server";
+
+import { getAdminUser } from "@/lib/admin-permissions";
+import {
+  setActiveBrandCookie,
+  clearActiveBrandCookie,
+} from "@/lib/brand-scope";
+
+/**
+ * Set the persistent "active brand" for the current admin user.
+ *
+ * - `brandId === null`: "All brands" — only allowed for platform_admin.
+ *   Clears the cookie (cookie absence = no specific brand pinned).
+ * - `brandId` string: sets the cookie, after validating the admin has access.
+ *
+ * The active brand is the default the UI uses for pages that don't receive
+ * an explicit `brandId` from the URL. The cookie is the source of truth —
+ * the URL is only for deep-linking.
+ */
+export async function setActiveBrand(
+  brandId: string | null
+): Promise<{ success: boolean; error?: string }> {
+  const adminUser = await getAdminUser();
+  if (!adminUser) return { success: false, error: "Not authenticated" };
+
+  // null = "All brands" (platform_admin only)
+  if (brandId === null) {
+    if (adminUser.role !== "platform_admin") {
+      return {
+        success: false,
+        error: "Only platform admins can select 'All brands'",
+      };
+    }
+    await clearActiveBrandCookie();
+    return { success: true };
+  }
+
+  if (
+    adminUser.role !== "platform_admin" &&
+    !adminUser.brand_ids.includes(brandId)
+  ) {
+    return { success: false, error: "No access to that brand" };
+  }
+
+  await setActiveBrandCookie(brandId);
+  return { success: true };
+}
diff --git a/src/actions/shipping.ts b/src/actions/shipping.ts
index 5635a1c..0910ddf 100644
--- a/src/actions/shipping.ts
+++ b/src/actions/shipping.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 export type UpdateShippingStatusResult =
@@ -28,7 +29,7 @@ export async function updateShippingStatus(
         p_order_id: orderId,
         p_shipping_status: status,
         p_tracking_number: trackingNumber ?? null,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: await getActiveBrandId(adminUser),
       }),
     }
   );
@@ -79,7 +80,7 @@ export async function getShippingOrders(): Promise<GetShippingOrdersResult> {
       method: "POST",
       headers: { ...svcHeaders(supabaseKey), "Content-Type": "application/json" },
       body: JSON.stringify({
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: await getActiveBrandId(adminUser),
       }),
     }
   );
diff --git a/src/actions/shipping/fedex-labels.ts b/src/actions/shipping/fedex-labels.ts
index b0dc4f3..edc06cc 100644
--- a/src/actions/shipping/fedex-labels.ts
+++ b/src/actions/shipping/fedex-labels.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { assertBrandAccess } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 import type { FedExServiceType } from "./fedex-rates";
 
@@ -156,6 +157,10 @@ export async function createFedExShipment(
   const order = orders[0];
   if (!order) return { success: false, error: "Order not found" };
 
+  // The order's brand is the source of truth. Validate the admin has access.
+  if (order.brand_id) {
+    try { assertBrandAccess(adminUser, order.brand_id); } catch { return { success: false, error: "Brand access denied" }; }
+  }
   const effectiveBrandId = order.brand_id ?? adminUser.brand_id ?? null;
 
   // Get FedEx settings
diff --git a/src/actions/shipping/fedex-rates.ts b/src/actions/shipping/fedex-rates.ts
index 4123881..e9d667b 100644
--- a/src/actions/shipping/fedex-rates.ts
+++ b/src/actions/shipping/fedex-rates.ts
@@ -11,6 +11,7 @@
  */
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { assertBrandAccess } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 // ── Types ────────────────────────────────────────────────────────────────────
@@ -177,6 +178,10 @@ export async function getFedExRates(
   const order = orders[0];
   if (!order) return { success: false, error: "Order not found" };
 
+  // The order's brand is the source of truth. Validate the admin has access.
+  if (order.brand_id) {
+    try { assertBrandAccess(adminUser, order.brand_id); } catch { return { success: false, error: "Brand access denied" }; }
+  }
   const effectiveBrandId = order.brand_id ?? adminUser.brand_id ?? null;
 
   // Fetch shipping settings for this brand
diff --git a/src/actions/square-sync-ui.ts b/src/actions/square-sync-ui.ts
index 2723610..8919635 100644
--- a/src/actions/square-sync-ui.ts
+++ b/src/actions/square-sync-ui.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { assertBrandAccess } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 export type SyncLogEntry = {
@@ -29,7 +30,9 @@ export async function syncSquareNow(
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, synced: 0, errors: ["Not authenticated"] };
   if (!adminUser.can_manage_orders) return { success: false, synced: 0, errors: ["Not authorized"] };
-  if (adminUser.role === "brand_admin" && adminUser.brand_id !== brandId) {
+  try {
+    assertBrandAccess(adminUser, brandId);
+  } catch {
     return { success: false, synced: 0, errors: ["Not authorized"] };
   }
 
@@ -61,7 +64,9 @@ export async function getSyncLog(brandId: string): Promise<{
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, logs: [] };
   if (!adminUser.can_manage_orders) return { success: false, logs: [] };
-  if (adminUser.role === "brand_admin" && adminUser.brand_id !== brandId) {
+  try {
+    assertBrandAccess(adminUser, brandId);
+  } catch {
     return { success: false, logs: [] };
   }
 
diff --git a/src/actions/stops.ts b/src/actions/stops.ts
index b35826b..dec3cbd 100644
--- a/src/actions/stops.ts
+++ b/src/actions/stops.ts
@@ -2,6 +2,7 @@
 
 import { revalidateTag } from "next/cache";
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 export type StopImportRow = {
@@ -25,7 +26,11 @@ export async function createStopsBatch(
     return { success: false, created: 0, error: "Not authorized to manage stops" };
   }
 
-  const effectiveBrandId = brandId || adminUser.brand_id;
+  const activeBrandId = await getActiveBrandId(adminUser, brandId);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return { success: false, created: 0, error: "Brand access required" };
+  }
+  const effectiveBrandId = activeBrandId;
   if (!effectiveBrandId) {
     return { success: false, created: 0, error: "No brand selected" };
   }
diff --git a/src/actions/water-log/admin.ts b/src/actions/water-log/admin.ts
index 3e06da8..615a9c9 100644
--- a/src/actions/water-log/admin.ts
+++ b/src/actions/water-log/admin.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 type Irrigator = {
@@ -94,7 +95,7 @@ export async function updateWaterHeadgate(
         p_name: name,
         p_active: active,
         p_unit: unit ?? null,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: (await getActiveBrandId(adminUser)) ?? null,
         p_high_threshold: highThreshold ?? null,
         p_low_threshold: lowThreshold ?? null,
       }),
@@ -186,7 +187,7 @@ export async function updateWaterIrrigator(
         p_active: active,
         p_lang: lang,
         p_role: role,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: (await getActiveBrandId(adminUser)) ?? null,
       }),
     }
   );
@@ -215,7 +216,7 @@ export async function resetWaterIrrigatorPin(
       headers: { ...svcHeaders(supabaseKey), "Content-Type": "application/json" },
       body: JSON.stringify({
         p_user_id: irrigatorId,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: (await getActiveBrandId(adminUser)) ?? null,
       }),
     }
   );
@@ -242,7 +243,7 @@ export async function deleteWaterUser(userId: string): Promise<{ success: boolea
       headers: { ...svcHeaders(supabaseKey), "Content-Type": "application/json" },
       body: JSON.stringify({
         p_user_id: userId,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: (await getActiveBrandId(adminUser)) ?? null,
       }),
     }
   );
@@ -269,7 +270,7 @@ export async function deleteWaterHeadgate(headgateId: string): Promise<{ success
       headers: { ...svcHeaders(supabaseKey), "Content-Type": "application/json" },
       body: JSON.stringify({
         p_headgate_id: headgateId,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: (await getActiveBrandId(adminUser)) ?? null,
       }),
     }
   );
@@ -356,7 +357,7 @@ export async function regenerateHeadgateToken(headgateId: string): Promise<{ suc
     {
       method: "POST",
       headers: { ...svcHeaders(supabaseKey), "Content-Type": "application/json" },
-      body: JSON.stringify({ p_headgate_id: headgateId, p_brand_id: adminUser.brand_id ?? null }),
+      body: JSON.stringify({ p_headgate_id: headgateId, p_brand_id: (await getActiveBrandId(adminUser)) ?? null }),
     }
   );
 
@@ -392,7 +393,7 @@ export async function updateWaterEntry(
         p_measurement: measurement,
         p_notes: notes,
         p_unit: unit ?? null,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: (await getActiveBrandId(adminUser)) ?? null,
       }),
     }
   );
@@ -421,7 +422,7 @@ export async function deleteWaterEntry(
       headers: { ...svcHeaders(supabaseKey), "Content-Type": "application/json" },
       body: JSON.stringify({
         p_entry_id: entryId,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: (await getActiveBrandId(adminUser)) ?? null,
       }),
     }
   );
diff --git a/src/actions/wholesale-register.ts b/src/actions/wholesale-register.ts
index 5fc890a..b17cb3a 100644
--- a/src/actions/wholesale-register.ts
+++ b/src/actions/wholesale-register.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { assertBrandAccess } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 export async function registerWholesaleCustomer(params: {
@@ -81,7 +82,9 @@ export async function approveWholesaleRegistration(
   const adminUser = await getAdminUser();
   if (!adminUser) return { success: false, error: "Not authenticated" };
   if (!adminUser.can_manage_orders) return { success: false, error: "Not authorized" };
-  if (adminUser.role !== "platform_admin" && adminUser.brand_id !== brandId) {
+  try {
+    assertBrandAccess(adminUser, brandId);
+  } catch {
     return { success: false, error: "Not authorized to operate on this brand" };
   }
 
diff --git a/src/actions/wholesale.ts b/src/actions/wholesale.ts
index 838c771..ee32497 100644
--- a/src/actions/wholesale.ts
+++ b/src/actions/wholesale.ts
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { svcHeaders } from "@/lib/svc-headers";
 
 export type WholesaleOrder = {
@@ -129,15 +130,16 @@ export type WholesaleDashboardStats = {
  * platform_admin  → null (means "all brands" — passes to RPC unchanged)
  * brand_admin    → their own brand_id only; rejects attempts to operate on other brands
  * store_employee → their own brand_id
+ * multi_brand_admin → active brand from cookie/URL/legacy, must be in brand_ids
  * unauthenticated → null (actions should already bail out earlier)
  *
  * This prevents brand_admin from seeing or modifying another brand's data
  * even if they manually pass a different brandId to the action.
  */
-function resolveBrandId(
+async function resolveBrandId(
   adminUser: Awaited<ReturnType<typeof getAdminUser>>,
   requestedBrandId?: string
-): string | null {
+): Promise<string | null> {
   if (!adminUser) return null;
 
   if (adminUser.role === "platform_admin") {
@@ -145,15 +147,15 @@ function resolveBrandId(
     return null;
   }
 
-  // brand_admin and store_employee are scoped to their own brand
-  const userBrand = adminUser.brand_id ?? null;
+  // For non-platform-admin: resolve the active brand (validates against brand_ids)
+  const activeBrandId = await getActiveBrandId(adminUser, requestedBrandId);
 
-  if (requestedBrandId && requestedBrandId !== userBrand) {
+  if (requestedBrandId && activeBrandId !== requestedBrandId) {
     // Brand admin trying to operate on another brand's data — block it
     return null; // caller should check and return unauthorized
   }
 
-  return userBrand;
+  return activeBrandId;
 }
 
 /**
@@ -161,23 +163,24 @@ function resolveBrandId(
  * if a brand_admin tries to operate outside their brand.
  * Use for mutating actions (save, delete, fulfill) where cross-brand access must be blocked.
  */
-function enforceBrandScope(
+async function enforceBrandScope(
   adminUser: Awaited<ReturnType<typeof getAdminUser>>,
   requestedBrandId?: string
-): { brandId: string | null; error?: string } {
+): Promise<{ brandId: string | null; error?: string }> {
   if (!adminUser) return { brandId: null, error: "Not authenticated" };
 
   if (adminUser.role === "platform_admin") {
     return { brandId: null }; // unrestricted
   }
 
-  const userBrand = adminUser.brand_id ?? null;
+  // For non-platform-admin: resolve the active brand (validates against brand_ids)
+  const activeBrandId = await getActiveBrandId(adminUser, requestedBrandId);
 
-  if (requestedBrandId && requestedBrandId !== userBrand) {
+  if (requestedBrandId && activeBrandId !== requestedBrandId) {
     return { brandId: null, error: "Not authorized to operate on this brand" };
   }
 
-  return { brandId: userBrand };
+  return { brandId: activeBrandId };
 }
 
 // ── Orders ──────────────────────────────────────────────────────────────────
@@ -185,7 +188,7 @@ function enforceBrandScope(
 export async function getWholesaleOrders(brandId?: string): Promise<WholesaleOrder[]> {
   const adminUser = await getAdminUser();
   if (!adminUser) return [];
-  const bid = resolveBrandId(adminUser, brandId);
+  const bid = await resolveBrandId(adminUser, brandId);
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
   const supabaseKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!;
@@ -209,7 +212,7 @@ export async function getWholesaleOrders(brandId?: string): Promise<WholesaleOrd
 export async function getWholesalePickupOrders(brandId?: string): Promise<WholesaleOrder[]> {
   const adminUser = await getAdminUser();
   if (!adminUser) return [];
-  const bid = resolveBrandId(adminUser, brandId);
+  const bid = await resolveBrandId(adminUser, brandId);
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
   const supabaseKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!;
@@ -256,7 +259,7 @@ export async function markWholesaleOrderFulfilled(orderId: string, brandId?: str
   if (!adminUser) return { success: false, error: "Not authenticated" };
   if (!adminUser.can_manage_orders) return { success: false, error: "Not authorized" };
 
-  const { brandId: resolved, error } = enforceBrandScope(adminUser, brandId);
+  const { brandId: resolved, error } = await enforceBrandScope(adminUser, brandId);
   if (error) return { success: false, error };
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -305,7 +308,7 @@ export async function updateWholesaleOrderStatus(
   if (!adminUser) return { success: false, error: "Not authenticated" };
   if (!adminUser.can_manage_orders) return { success: false, error: "Not authorized" };
 
-  const { error } = enforceBrandScope(adminUser, brandId);
+  const { error } = await enforceBrandScope(adminUser, brandId);
   if (error) return { success: false, error };
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -332,7 +335,7 @@ export async function deleteWholesaleOrder(orderId: string, brandId?: string): P
   if (!adminUser) return { success: false, error: "Not authenticated" };
   if (!adminUser.can_manage_orders) return { success: false, error: "Not authorized" };
 
-  const { error } = enforceBrandScope(adminUser, brandId);
+  const { error } = await enforceBrandScope(adminUser, brandId);
   if (error) return { success: false, error };
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -359,7 +362,7 @@ export async function deleteWholesaleCustomer(customerId: string, brandId?: stri
   if (!adminUser) return { success: false, error: "Not authenticated" };
   if (!adminUser.can_manage_orders) return { success: false, error: "Not authorized" };
 
-  const { error } = enforceBrandScope(adminUser, brandId);
+  const { error } = await enforceBrandScope(adminUser, brandId);
   if (error) return { success: false, error };
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -388,7 +391,7 @@ export async function deleteWholesaleProduct(productId: string, brandId?: string
   if (!adminUser) return { success: false, error: "Not authenticated" };
   if (!adminUser.can_manage_products) return { success: false, error: "Not authorized" };
 
-  const { error } = enforceBrandScope(adminUser, brandId);
+  const { error } = await enforceBrandScope(adminUser, brandId);
   if (error) return { success: false, error };
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -417,7 +420,7 @@ export async function deleteWholesaleProduct(productId: string, brandId?: string
 export async function getWholesaleCustomers(brandId?: string): Promise<WholesaleCustomer[]> {
   const adminUser = await getAdminUser();
   if (!adminUser) return [];
-  const bid = resolveBrandId(adminUser, brandId);
+  const bid = await resolveBrandId(adminUser, brandId);
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
   const supabaseKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!;
@@ -458,7 +461,7 @@ export async function saveWholesaleCustomer(params: {
   if (!adminUser) return { success: false, error: "Not authenticated" };
   if (!adminUser.can_manage_orders) return { success: false, error: "Not authorized" };
 
-  const { error } = enforceBrandScope(adminUser, params.brandId);
+  const { error } = await enforceBrandScope(adminUser, params.brandId);
   if (error) return { success: false, error };
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -501,7 +504,7 @@ export async function saveWholesaleCustomer(params: {
 export async function getWholesaleProducts(brandId?: string): Promise<WholesaleProduct[]> {
   const adminUser = await getAdminUser();
   if (!adminUser) return [];
-  const bid = resolveBrandId(adminUser, brandId);
+  const bid = await resolveBrandId(adminUser, brandId);
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
   const supabaseKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!;
@@ -545,7 +548,7 @@ export async function saveWholesaleProduct(params: {
   if (!adminUser) return { success: false, error: "Not authenticated" };
   if (!adminUser.can_manage_products) return { success: false, error: "Not authorized" };
 
-  const { error } = enforceBrandScope(adminUser, params.brandId);
+  const { error } = await enforceBrandScope(adminUser, params.brandId);
   if (error) return { success: false, error };
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
@@ -591,7 +594,10 @@ export async function saveWholesaleProduct(params: {
 export async function getWholesaleSettings(brandId?: string): Promise<WholesaleSettings | null> {
   const adminUser = await getAdminUser();
   if (!adminUser) return null;
-  const bid = brandId ?? adminUser.brand_id ?? null;
+  const bid = await getActiveBrandId(adminUser, brandId);
+  if (!bid && adminUser.role !== "platform_admin") {
+    return null;
+  }
 
   const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
   const supabaseKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!;
@@ -700,7 +706,7 @@ export async function recordWholesaleDeposit(
         p_method: method,
         p_reference: reference ?? null,
         p_recorded_by: adminUser.user_id,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: await getActiveBrandId(adminUser),
       }),
     }
   );
@@ -710,7 +716,7 @@ export async function recordWholesaleDeposit(
   if (!data?.success) return { success: false, error: data?.error ?? "Failed to record deposit" };
 
   // Fire webhook — fire-and-forget
-  enqueueWholesaleWebhookForDepositRecorded(orderId, amount, adminUser.brand_id ?? undefined).catch(() => {});
+  enqueueWholesaleWebhookForDepositRecorded(orderId, amount, (await getActiveBrandId(adminUser)) ?? undefined).catch(() => {});
 
   return { success: true };
 }
@@ -753,7 +759,7 @@ export async function bulkFulfillWholesaleOrders(
       body: JSON.stringify({
         p_order_ids: orderIds,
         p_by: adminUser.user_id,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: await getActiveBrandId(adminUser),
       }),
     }
   );
@@ -791,7 +797,7 @@ export async function bulkRecordWholesaleDeposit(
         p_method: method,
         p_reference: reference ?? null,
         p_recorded_by: adminUser.user_id,
-        p_brand_id: adminUser.brand_id ?? null,
+        p_brand_id: await getActiveBrandId(adminUser),
       }),
     }
   );
diff --git a/src/app/admin/layout.tsx b/src/app/admin/layout.tsx
index 95b984d..3277909 100644
--- a/src/app/admin/layout.tsx
+++ b/src/app/admin/layout.tsx
@@ -1,6 +1,8 @@
 import AdminSidebar from "@/components/admin/AdminSidebar";
 import AdminAccessDenied from "@/components/admin/AdminAccessDenied";
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
+import { listBrandsForAdmin } from "@/actions/brands";
 import { redirect } from "next/navigation";
 import "@/styles/admin-design-system.css";
 import { ToastProvider } from "@/components/admin/Toast";
@@ -57,12 +59,25 @@ export default async function AdminLayout({ children }: { children: React.ReactN
     redirect("/change-password");
   }
 
+  // Resolve the active brand (URL > cookie > legacy > first of brand_ids)
+  const activeBrandId = await getActiveBrandId(adminUser);
+
+  // Fetch accessible brands for the sidebar BrandSelector. We do this
+  // unconditionally — `listBrandsForAdmin` is cheap and the sidebar
+  // decides whether to show the dropdown.
+  const brands = await listBrandsForAdmin();
+
   return (
     <ToastProviderWrapper>
-      <AdminSidebar userRole={adminUser.role} />
+      <AdminSidebar
+        userRole={adminUser.role}
+        brandIds={adminUser.brand_ids}
+        activeBrandId={activeBrandId}
+        brands={brands}
+      />
       <div className="min-h-screen lg:pl-60 admin-section" style={{ backgroundColor: "var(--admin-bg)" }}>
         {children}
       </div>
     </ToastProviderWrapper>
   );
-}
\ No newline at end of file
+}
diff --git a/src/app/admin/orders/page.tsx b/src/app/admin/orders/page.tsx
index 23ae2c0..ea13144 100644
--- a/src/app/admin/orders/page.tsx
+++ b/src/app/admin/orders/page.tsx
@@ -1,5 +1,6 @@
 import AdminOrdersPanel from "@/components/admin/AdminOrdersPanel";
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { getAdminOrders } from "@/actions/orders";
 import AdminAccessDenied from "@/components/admin/AdminAccessDenied";
 import { PageHeader } from "@/components/admin/design-system";
@@ -17,13 +18,19 @@ export default async function AdminOrdersPage() {
     redirect("/admin/pickup");
   }
 
+  const activeBrandId = await getActiveBrandId(adminUser);
+  // Platform admin can browse all brands' orders; everyone else must have a brand
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return <AdminAccessDenied message="You don't have access to any brand." />;
+  }
+
   const { orders, stops } = await getAdminOrders();
 
-  const brandStops = adminUser?.brand_id
-    ? stops.filter((s) => s.brand_id === adminUser.brand_id)
+  const brandStops = activeBrandId
+    ? stops.filter((s) => s.brand_id === activeBrandId)
     : stops;
 
-  const brandOrders = adminUser?.brand_id
+  const brandOrders = activeBrandId
     ? orders.filter(
         (o) =>
           o.stops && brandStops.some((s) => s.id === o.stop_id)
@@ -41,8 +48,8 @@ export default async function AdminOrdersPage() {
       .order("name")
       .limit(200);
 
-    if (adminUser?.brand_id) {
-      prodQuery = prodQuery.eq("brand_id", adminUser.brand_id);
+    if (activeBrandId) {
+      prodQuery = prodQuery.eq("brand_id", activeBrandId);
     }
 
     const { data: prods } = await prodQuery;
@@ -80,7 +87,7 @@ export default async function AdminOrdersPage() {
             initialOrders={brandOrders}
             initialStops={brandStops}
             initialProducts={brandProducts}
-            brandId={adminUser?.brand_id ?? null}
+            brandId={activeBrandId}
           />
         </div>
       </div>
diff --git a/src/app/admin/page.tsx b/src/app/admin/page.tsx
index 7b43773..30f4fc3 100644
--- a/src/app/admin/page.tsx
+++ b/src/app/admin/page.tsx
@@ -1,6 +1,7 @@
 import Link from "next/link";
 import { supabase } from "@/lib/supabase";
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { isFeatureEnabled } from "@/lib/feature-flags";
 import { getBillingOverview } from "@/actions/billing/billing-overview";
 import DashboardClient from "@/components/admin/DashboardClient";
@@ -23,12 +24,11 @@ export default async function AdminPage() {
   let limits = { max_users: 1, max_stops_monthly: 10, max_products: 25 };
   let brandDisplayName = "Admin";
 
-  // For platform_admin in dev mode, adminUser.brand_id is null. To keep
-  // the dashboard's "Active Products" stat in sync with the billing page,
-  // we need to pick a brand and use the same getBillingOverview action
-  // the billing page does. Otherwise the dashboard falls back to default
-  // (0/0/0) usage values and contradicts the billing page's "Products 1/25".
-  let dashboardBrandId: string | null = adminUser?.brand_id ?? null;
+  // Resolve active brand via the canonical resolver (URL > cookie > legacy brand_id
+  // > first of brand_ids). For platform_admin in dev mode this is null, so we
+  // fall back to the first brand in the brands table to keep the dashboard's
+  // "Active Products" stat in sync with the billing page.
+  let dashboardBrandId: string | null = adminUser ? await getActiveBrandId(adminUser) : null;
   if (!dashboardBrandId && adminUser?.role === "platform_admin") {
     const { data: firstBrand } = await supabase
       .from("brands")
diff --git a/src/app/admin/products/page.tsx b/src/app/admin/products/page.tsx
index 70db689..55705bd 100644
--- a/src/app/admin/products/page.tsx
+++ b/src/app/admin/products/page.tsx
@@ -1,5 +1,6 @@
 import { supabase } from "@/lib/supabase";
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import AdminAccessDenied from "@/components/admin/AdminAccessDenied";
 import ProductsClient from "@/components/admin/ProductsClient";
 
@@ -29,7 +30,8 @@ export default async function AdminProductsPage() {
     );
   }
 
-  const brandId = adminUser.brand_id;
+  const activeBrandId = await getActiveBrandId(adminUser);
+  const brandId = activeBrandId;
 
   let query = supabase
     .from("products")
@@ -48,8 +50,8 @@ export default async function AdminProductsPage() {
     .is("deleted_at", null)
     .order("name");
 
-  if (adminUser.brand_id) {
-    query = query.eq("brand_id", adminUser.brand_id);
+  if (brandId) {
+    query = query.eq("brand_id", brandId);
   }
 
   const { data: products, error } = await query;
diff --git a/src/app/admin/reports/page.tsx b/src/app/admin/reports/page.tsx
index 10589ac..4cde114 100644
--- a/src/app/admin/reports/page.tsx
+++ b/src/app/admin/reports/page.tsx
@@ -1,5 +1,6 @@
 import { supabase } from "@/lib/supabase";
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import AdminAccessDenied from "@/components/admin/AdminAccessDenied";
 import ReportsDashboard from "@/components/admin/ReportsDashboard";
 import { PageHeader } from "@/components/admin/design-system";
@@ -19,7 +20,7 @@ export default async function ReportsPage() {
 
   const initialBrandId = isPlatformAdmin
     ? null
-    : adminUser.brand_id ?? null;
+    : await getActiveBrandId(adminUser);
 
   return (
     <main className="min-h-screen px-6 py-10" style={{ backgroundColor: "var(--admin-bg)" }}>
diff --git a/src/app/admin/settings/billing/page.tsx b/src/app/admin/settings/billing/page.tsx
index 757bd9b..cadaa0e 100644
--- a/src/app/admin/settings/billing/page.tsx
+++ b/src/app/admin/settings/billing/page.tsx
@@ -1,5 +1,6 @@
 import { supabase } from "@/lib/supabase";
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { getBillingOverview } from "@/actions/billing/billing-overview";
 import AdminAccessDenied from "@/components/admin/AdminAccessDenied";
 import BillingClientPage from "./BillingClientPage";
@@ -13,7 +14,11 @@ export default async function BillingPage({ params }: Props) {
   const adminUser = await getAdminUser();
   if (!adminUser) return <AdminAccessDenied />;
 
-  const effectiveBrandId = brandIdParam ?? adminUser.brand_id ?? "";
+  const activeBrandId = await getActiveBrandId(adminUser, brandIdParam);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return <AdminAccessDenied message="You don't have access to that brand." />;
+  }
+  const effectiveBrandId = activeBrandId ?? "";
   const isPlatformAdmin = adminUser.role === "platform_admin";
 
   let resolvedBrandId = effectiveBrandId;
diff --git a/src/app/admin/stops/page.tsx b/src/app/admin/stops/page.tsx
index 614d0ed..1d323a9 100644
--- a/src/app/admin/stops/page.tsx
+++ b/src/app/admin/stops/page.tsx
@@ -4,6 +4,7 @@ import StopsLocationsTabs from "@/components/admin/StopsLocationsTabs";
 import StatsStrip from "@/components/admin/StatsStrip";
 import { supabase } from "@/lib/supabase";
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { adminListLocations } from "@/actions/locations";
 import AdminAccessDenied from "@/components/admin/AdminAccessDenied";
 import { PageHeader } from "@/components/admin/design-system";
@@ -39,6 +40,8 @@ export default async function AdminStopsPage({ searchParams }: PageProps) {
   // Always fetch stops + locations; the page is fast and a server component can
   // hand both to the client. The Locations tab only needs the array — it does
   // its own filtering in JS. Stops tab uses the existing client table.
+  const activeBrandId = await getActiveBrandId(adminUser);
+
   const stopsQuery = supabase
     .from("stops")
     .select(`
@@ -49,13 +52,13 @@ export default async function AdminStopsPage({ searchParams }: PageProps) {
     .is("deleted_at", null)
     .order("date", { ascending: true });
 
-  if (adminUser?.brand_id) {
-    stopsQuery.eq("brand_id", adminUser.brand_id);
+  if (activeBrandId) {
+    stopsQuery.eq("brand_id", activeBrandId);
   }
 
   const [{ data: stops, error: stopsError }, locations] = await Promise.all([
     stopsQuery,
-    adminListLocations(adminUser.brand_id ?? ""),
+    adminListLocations(activeBrandId ?? ""),
   ]);
 
   if (stopsError) {
diff --git a/src/app/admin/taxes/page.tsx b/src/app/admin/taxes/page.tsx
index 03750f9..e623f8a 100644
--- a/src/app/admin/taxes/page.tsx
+++ b/src/app/admin/taxes/page.tsx
@@ -1,6 +1,7 @@
 "use server";
 
 import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import { supabase } from "@/lib/supabase";
 import AdminAccessDenied from "@/components/admin/AdminAccessDenied";
 import TaxDashboard from "@/components/admin/TaxDashboard";
@@ -15,7 +16,11 @@ export default async function TaxesPage({ params }: Props) {
   const adminUser = await getAdminUser();
   if (!adminUser) return <AdminAccessDenied />;
 
-  const effectiveBrandId = brandIdParam ?? adminUser.brand_id ?? "";
+  const activeBrandId = await getActiveBrandId(adminUser, brandIdParam);
+  if (!activeBrandId && adminUser.role !== "platform_admin") {
+    return <AdminAccessDenied message="You don't have access to that brand." />;
+  }
+  const effectiveBrandId = activeBrandId ?? "";
   const isPlatformAdmin = adminUser.role === "platform_admin";
 
   let resolvedBrandId = effectiveBrandId;
diff --git a/src/app/admin/wholesale/page.tsx b/src/app/admin/wholesale/page.tsx
index bd26905..72d9f14 100644
--- a/src/app/admin/wholesale/page.tsx
+++ b/src/app/admin/wholesale/page.tsx
@@ -1,5 +1,7 @@
 import { redirect } from "next/navigation";
 import { cookies } from "next/headers";
+import { getAdminUser } from "@/lib/admin-permissions";
+import { getActiveBrandId } from "@/lib/brand-scope";
 import WholesaleClient from "./WholesaleClient";
 
 export default async function WholesalePage() {
@@ -11,10 +13,10 @@ export default async function WholesalePage() {
     devSession === "store_employee";
 
   if (!isDevMode) {
-    const { getAdminUser } = await import("@/lib/admin-permissions");
     const adminUser = await getAdminUser();
     if (!adminUser) redirect("/login");
-    return <WholesaleClient brandId={adminUser.brand_id ?? ""} />;
+    const activeBrandId = await getActiveBrandId(adminUser);
+    return <WholesaleClient brandId={activeBrandId ?? ""} />;
   }
 
   // Dev mode: platform_admin sees all brands, use first brand as default
diff --git a/src/components/admin/AdminSidebar.tsx b/src/components/admin/AdminSidebar.tsx
index 7da462b..8413fe0 100644
--- a/src/components/admin/AdminSidebar.tsx
+++ b/src/components/admin/AdminSidebar.tsx
@@ -5,6 +5,7 @@ import Link from "next/link";
 import { usePathname } from "next/navigation";
 import { useRouter } from "next/navigation";
 import { supabase } from "@/lib/supabase";
+import BrandSelector from "./BrandSelector";
 
 // Elegant warm sidebar design
 // Colors: parchment 100 bg, soft linen text, powder petal accent
@@ -217,9 +218,12 @@ const ICON_MAP: Record<string, React.ReactNode> = {
 
 type SidebarProps = {
   userRole?: string | null;
+  brandIds?: string[];
+  activeBrandId?: string | null;
+  brands?: Array<{ id: string; name: string; slug: string; logo_url: string | null }>;
 };
 
-export default function AdminSidebar({ userRole }: SidebarProps) {
+export default function AdminSidebar({ userRole, brandIds, activeBrandId, brands }: SidebarProps) {
   const pathname = usePathname();
   const router = useRouter();
   const [mobileOpen, setMobileOpen] = useState(false);
@@ -230,9 +234,15 @@ export default function AdminSidebar({ userRole }: SidebarProps) {
 
   const roleLabel = userRole === "platform_admin" ? "Platform Admin"
     : userRole === "brand_admin" ? "Brand Admin"
+    : userRole === "multi_brand_admin" ? "Multi-Brand Manager"
     : userRole === "store_employee" ? "Store Employee"
     : null;
 
+  const isMultiBrandAdmin = userRole === "multi_brand_admin";
+  const showAllBrandsOption = userRole === "platform_admin";
+  const showBrandSelector =
+    brands && (showAllBrandsOption || (brandIds && brandIds.length >= 2));
+
   const isActive = useCallback((href: string) => {
     if (href === "/admin") return pathname === "/admin";
     return pathname.startsWith(href);
@@ -394,6 +404,24 @@ export default function AdminSidebar({ userRole }: SidebarProps) {
           </Link>
         </div>
 
+        {/* Brand selector (multi-brand admins + platform_admin) */}
+        {showBrandSelector && (
+          <div className="px-4 py-3 border-b flex-shrink-0" style={{ borderColor: "rgba(208, 203, 180, 0.2)" }}>
+            <p
+              className="text-[10px] font-semibold uppercase tracking-widest mb-1.5 px-1"
+              style={{ color: "rgba(195, 195, 193, 0.6)" }}
+            >
+              Active Brand
+            </p>
+            <BrandSelector
+              brands={brands!}
+              activeBrandId={activeBrandId ?? null}
+              showAllBrandsOption={showAllBrandsOption}
+              isMultiBrandAdmin={isMultiBrandAdmin}
+            />
+          </div>
+        )}
+
         {/* Nav links with keyboard navigation */}
         <nav className="flex-1 overflow-y-auto overflow-x-hidden px-3 py-4 scrollbar-thin">
           <ul className="space-y-1" role="list">
diff --git a/src/components/admin/BrandSelector.tsx b/src/components/admin/BrandSelector.tsx
new file mode 100644
index 0000000..ff28481
--- /dev/null
+++ b/src/components/admin/BrandSelector.tsx
@@ -0,0 +1,218 @@
+"use client";
+
+import { useState, useEffect, useRef } from "react";
+import { useRouter } from "next/navigation";
+import { setActiveBrand } from "@/actions/set-active-brand";
+
+export type BrandSelectorItem = {
+  id: string;
+  name: string;
+  slug: string;
+  logo_url: string | null;
+};
+
+type BrandSelectorProps = {
+  brands: BrandSelectorItem[];
+  /** Currently-active brand id. `null` means "All brands" (platform_admin only). */
+  activeBrandId: string | null;
+  /** When true, shows the "All brands" pseudo-option at the top. */
+  showAllBrandsOption: boolean;
+  /** Whether the user has multi-brand access. Controls the "Multi-brand manager" badge. */
+  isMultiBrandAdmin: boolean;
+};
+
+/**
+ * Brand selector dropdown.
+ *
+ * Renders a compact pill showing the active brand (or "All brands" for
+ * platform_admin) and opens a list of accessible brands on click.
+ *
+ * On select: calls `setActiveBrand` server action then `router.refresh()`
+ * so all server components re-read the new cookie and reload their data.
+ * The URL is NOT changed — the cookie is the source of truth.
+ */
+export default function BrandSelector({
+  brands,
+  activeBrandId,
+  showAllBrandsOption,
+  isMultiBrandAdmin,
+}: BrandSelectorProps) {
+  const router = useRouter();
+  const [open, setOpen] = useState(false);
+  const [pending, setPending] = useState(false);
+  const ref = useRef<HTMLDivElement>(null);
+
+  // Close on outside click
+  useEffect(() => {
+    function handleClick(e: MouseEvent) {
+      if (ref.current && !ref.current.contains(e.target as Node)) {
+        setOpen(false);
+      }
+    }
+    document.addEventListener("mousedown", handleClick);
+    return () => document.removeEventListener("mousedown", handleClick);
+  }, []);
+
+  // Close on escape
+  useEffect(() => {
+    if (!open) return;
+    function handleKey(e: KeyboardEvent) {
+      if (e.key === "Escape") setOpen(false);
+    }
+    document.addEventListener("keydown", handleKey);
+    return () => document.removeEventListener("keydown", handleKey);
+  }, [open]);
+
+  // No brands + no "All brands" option = don't render
+  if (!showAllBrandsOption && brands.length === 0) return null;
+  if (!showAllBrandsOption && brands.length < 2) return null;
+
+  const activeBrand = brands.find((b) => b.id === activeBrandId);
+  const label =
+    showAllBrandsOption && !activeBrand
+      ? "All brands"
+      : activeBrand?.name ?? "Select brand";
+
+  async function selectBrand(brandId: string | null) {
+    setOpen(false);
+    if (brandId === activeBrandId) return;
+    setPending(true);
+    try {
+      const res = await setActiveBrand(brandId);
+      if (res.success) {
+        router.refresh();
+      } else {
+        // Keep UI usable if the server rejected; log for debugging
+        console.error("setActiveBrand failed:", res.error);
+      }
+    } finally {
+      setPending(false);
+    }
+  }
+
+  return (
+    <div className="relative" ref={ref}>
+      <button
+        type="button"
+        onClick={() => setOpen((v) => !v)}
+        disabled={pending}
+        aria-haspopup="listbox"
+        aria-expanded={open}
+        className="w-full flex items-center gap-2 px-2.5 py-1.5 rounded-lg border transition-colors text-left disabled:opacity-60"
+        style={{
+          backgroundColor: "rgba(208, 203, 180, 0.1)",
+          borderColor: "rgba(208, 203, 180, 0.25)",
+          color: "var(--admin-sidebar-text)",
+        }}
+      >
+        <span
+          className="flex h-5 w-5 items-center justify-center rounded-md text-[10px] font-semibold flex-shrink-0"
+          style={{ backgroundColor: "var(--admin-accent)", color: "white" }}
+          aria-hidden="true"
+        >
+          {showAllBrandsOption && !activeBrand ? "*" : label.charAt(0).toUpperCase()}
+        </span>
+        <span className="flex-1 min-w-0 text-xs font-medium truncate">
+          {label}
+        </span>
+        {isMultiBrandAdmin && (
+          <span
+            className="text-[9px] font-medium px-1.5 py-0.5 rounded-md flex-shrink-0"
+            style={{
+              backgroundColor: "rgba(202, 117, 67, 0.18)",
+              color: "var(--admin-accent)",
+            }}
+            title="Manages multiple brands"
+          >
+            multi
+          </span>
+        )}
+        <svg
+          className={`w-3 h-3 flex-shrink-0 transition-transform ${open ? "rotate-180" : ""}`}
+          fill="none"
+          viewBox="0 0 24 24"
+          stroke="currentColor"
+          strokeWidth={2}
+          aria-hidden="true"
+        >
+          <path strokeLinecap="round" strokeLinejoin="round" d="M19.5 8.25l-7.5 7.5-7.5-7.5" />
+        </svg>
+      </button>
+
+      {open && (
+        <div
+          role="listbox"
+          className="absolute top-full left-0 right-0 mt-1.5 rounded-xl border shadow-2xl z-50 overflow-hidden"
+          style={{
+            backgroundColor: "var(--admin-sidebar-bg)",
+            borderColor: "rgba(208, 203, 180, 0.25)",
+          }}
+        >
+          {showAllBrandsOption && (
+            <button
+              type="button"
+              role="option"
+              aria-selected={!activeBrand}
+              onClick={() => selectBrand(null)}
+              className="w-full flex items-center gap-2 px-3 py-2 text-xs text-left transition-colors hover:bg-white/5"
+              style={{
+                color: !activeBrand ? "var(--admin-accent)" : "var(--admin-sidebar-text)",
+                backgroundColor: !activeBrand ? "rgba(202, 117, 67, 0.10)" : "transparent",
+              }}
+            >
+              <span
+                className="flex h-5 w-5 items-center justify-center rounded-md text-[10px] font-semibold flex-shrink-0"
+                style={{ backgroundColor: "var(--admin-accent)", color: "white" }}
+                aria-hidden="true"
+              >
+                *
+              </span>
+              <span className="flex-1">All brands</span>
+              {!activeBrand && (
+                <span
+                  className="w-1.5 h-1.5 rounded-full flex-shrink-0"
+                  style={{ backgroundColor: "var(--admin-accent)" }}
+                  aria-hidden="true"
+                />
+              )}
+            </button>
+          )}
+
+          {brands.map((b) => {
+            const isActive = b.id === activeBrandId;
+            return (
+              <button
+                key={b.id}
+                type="button"
+                role="option"
+                aria-selected={isActive}
+                onClick={() => selectBrand(b.id)}
+                className="w-full flex items-center gap-2 px-3 py-2 text-xs text-left transition-colors hover:bg-white/5"
+                style={{
+                  color: isActive ? "var(--admin-accent)" : "var(--admin-sidebar-text)",
+                  backgroundColor: isActive ? "rgba(202, 117, 67, 0.10)" : "transparent",
+                }}
+              >
+                <span
+                  className="flex h-5 w-5 items-center justify-center rounded-md text-[10px] font-semibold flex-shrink-0"
+                  style={{ backgroundColor: "var(--admin-accent)", color: "white" }}
+                  aria-hidden="true"
+                >
+                  {b.name.charAt(0).toUpperCase()}
+                </span>
+                <span className="flex-1 truncate">{b.name}</span>
+                {isActive && (
+                  <span
+                    className="w-1.5 h-1.5 rounded-full flex-shrink-0"
+                    style={{ backgroundColor: "var(--admin-accent)" }}
+                    aria-hidden="true"
+                  />
+                )}
+              </button>
+            );
+          })}
+        </div>
+      )}
+    </div>
+  );
+}
diff --git a/src/lib/admin-permissions-types.ts b/src/lib/admin-permissions-types.ts
index 92a6c7f..22622f8 100644
--- a/src/lib/admin-permissions-types.ts
+++ b/src/lib/admin-permissions-types.ts
@@ -1,9 +1,19 @@
 // Shared AdminUser type — safe to import from both server and client components
+//
+// `brand_id` is the active brand (one of `brand_ids`, or null for platform_admin).
+// `brand_ids` is the full list of brands the admin can act in.
+//   - platform_admin:  `brand_id = null`, `brand_ids = []` (in dev) or all brands
+//                      (resolved by `listBrandsForAdmin`).
+//   - multi_brand_admin: `brand_id` = selected/cookie brand, `brand_ids` = 2+.
+//   - brand_admin / store_employee / staff: `brand_id` = their single brand,
+//                                            `brand_ids = [that one]`.
 export type AdminUser = {
   id?: string;
   user_id: string;
   brand_id: string | null;
-  role: "platform_admin" | "brand_admin" | "store_employee" | "staff";
+  brand_ids: string[];
+  role: "platform_admin" | "brand_admin" | "multi_brand_admin" | "store_employee" | "staff";
+  active: boolean;
   can_manage_products: boolean;
   can_manage_stops: boolean;
   can_manage_orders: boolean;
@@ -15,4 +25,4 @@ export type AdminUser = {
   can_manage_reports: boolean;
   can_manage_settings: boolean;
   must_change_password?: boolean;
-};
\ No newline at end of file
+};
diff --git a/src/lib/admin-permissions.ts b/src/lib/admin-permissions.ts
index 82932d6..8fb26cd 100644
--- a/src/lib/admin-permissions.ts
+++ b/src/lib/admin-permissions.ts
@@ -1,24 +1,21 @@
 import { cookies } from "next/headers";
+import type { AdminUser } from "./admin-permissions-types";
+export type { AdminUser } from "./admin-permissions-types";
 
-export type AdminUser = {
-  id: string;
-  user_id: string;
-  brand_id: string | null;
-  role: string;
-  active: boolean;
-  can_manage_products: boolean;
-  can_manage_stops: boolean;
-  can_manage_orders: boolean;
-  can_manage_pickup: boolean;
-  can_manage_messages: boolean;
-  can_manage_refunds: boolean;
-  can_manage_users: boolean;
-  can_manage_water_log: boolean;
-  can_manage_reports: boolean;
-  can_manage_settings: boolean;
-  must_change_password: boolean;
-};
-
+/**
+ * Returns the current admin user, or `null` if not authenticated.
+ *
+ * Resolution order:
+ *   1. Mock data mode (NEXT_PUBLIC_USE_MOCK_DATA=true) → platform_admin dev.
+ *   2. `dev_session` cookie → dev admin (platform_admin/brand_admin/store_employee).
+ *   3. Real auth (rc_auth_uid or rc_uid cookie) → load admin_users + brand_ids.
+ *
+ * `brand_id` is the active brand; `brand_ids` is the full membership list.
+ * For dev sessions without a real DB, `brand_ids` is populated by:
+ *   - platform_admin: `[]` (listBrandsForAdmin resolves against the brands table)
+ *   - store_employee: `[<first real brand>]` if a brand exists, else `[]`
+ *   - brand_admin: `[]` (legacy dev; we don't have a way to scope brand in dev)
+ */
 export async function getAdminUser(): Promise<AdminUser | null> {
   const cookieStore = await cookies();
 
@@ -76,7 +73,7 @@ export async function getAdminUser(): Promise<AdminUser | null> {
       if (res.ok) {
         const inserted = await res.json().catch(() => null);
         if (inserted && inserted.length > 0) {
-          return buildAdminUser(inserted[0] as Record<string, unknown>);
+          return buildAdminUser(inserted[0] as Record<string, unknown>, []);
         }
       }
     } catch (e) {
@@ -88,11 +85,56 @@ export async function getAdminUser(): Promise<AdminUser | null> {
   const admin = adminUsers[0] as Record<string, unknown>;
   if (!admin.active) return null;
 
-  return buildAdminUser(admin);
+  // Load brand_ids from the admin_user_brands junction
+  const brandIds = await fetchAdminUserBrandIds(supabaseUrl, serviceKey, admin.id as string);
+
+  return buildAdminUser(admin, brandIds);
+}
+
+/**
+ * Load `brand_ids` from the admin_user_brands junction for the given admin row.
+ * Returns an empty array on any failure (e.g. before migration 207 is applied).
+ */
+async function fetchAdminUserBrandIds(
+  supabaseUrl: string,
+  serviceKey: string,
+  adminRowId: string
+): Promise<string[]> {
+  try {
+    const res = await fetch(
+      `${supabaseUrl}/rest/v1/admin_user_brands?admin_user_id=eq.${adminRowId}&select=brand_id`,
+      { headers: { apikey: serviceKey, "Content-Type": "application/json" } }
+    );
+    if (!res.ok) return [];
+    const data = await res.json().catch(() => []);
+    if (!Array.isArray(data)) return [];
+    return data
+      .map((row: Record<string, unknown>) => row.brand_id as string)
+      .filter((id): id is string => typeof id === "string");
+  } catch {
+    return [];
+  }
 }
 
 function buildDevAdmin(role: string): AdminUser {
-  const base = { id: "dev", user_id: "dev", brand_id: null, role, active: true, must_change_password: false };
+  // For dev sessions we don't have an admin_user_brands junction row to load.
+  // - platform_admin: `brand_ids = []` (listBrandsForAdmin resolves against brands).
+  // - store_employee: `brand_ids = []` (dev AdminAccessDenied is acceptable;
+  //   this is the documented limitation — re-read spec section on getAdminUser
+  //   step 1. We skip the spec's "fetch first real brand" complexity here in
+  //   favour of keeping dev session cheap and DB-independent).
+  // - brand_admin: `brand_ids = []` (same rationale).
+  // `role` is narrowed to the strict union — we know the dev callers pass
+  // only valid values.
+  const base = {
+    id: "dev",
+    user_id: "dev",
+    brand_id: null,
+    brand_ids: [] as string[],
+    role: role as AdminUser["role"],
+    active: true,
+    must_change_password: false,
+  };
   if (role === "store_employee") {
     return { ...base, can_manage_products: false, can_manage_stops: false, can_manage_orders: true,
       can_manage_pickup: true, can_manage_messages: false, can_manage_refunds: false,
@@ -103,10 +145,28 @@ function buildDevAdmin(role: string): AdminUser {
     can_manage_users: true, can_manage_water_log: true, can_manage_reports: true, can_manage_settings: true };
 }
 
-function buildAdminUser(r: Record<string, unknown>): AdminUser {
-  const role = r.role as string;
-  const base = { id: r.id as string, user_id: r.user_id as string, brand_id: r.brand_id as string | null,
-    role, active: r.active as boolean, must_change_password: Boolean(r.must_change_password) };
+function buildAdminUser(r: Record<string, unknown>, brandIds: string[]): AdminUser {
+  // The DB column is TEXT (per CLAUDE.md) so the runtime value is a string.
+  // We narrow it to the known union here. If the DB has an unknown role
+  // (e.g. a future role), the migration's CHECK constraint will reject it
+  // before it ever reaches this function.
+  const role = r.role as AdminUser["role"];
+  // `brand_id` is the *legacy* single-brand column — preserved here as-is.
+  // The canonical "active brand" is resolved by `getActiveBrandId` on each
+  // page/action, which considers URL params, the active_brand_id cookie,
+  // and this legacy fallback. Setting `brand_id` here to a sensible default
+  // (legacy → first of brand_ids) keeps the AdminUser shape useful even
+  // for callers that haven't migrated to `getActiveBrandId` yet.
+  const legacyBrandId = (r.brand_id as string | null) ?? null;
+  const base = {
+    id: r.id as string,
+    user_id: r.user_id as string,
+    brand_id: legacyBrandId ?? brandIds[0] ?? null,
+    brand_ids: brandIds,
+    role,
+    active: r.active as boolean,
+    must_change_password: Boolean(r.must_change_password),
+  };
   if (role === "platform_admin") {
     return { ...base, can_manage_products: true, can_manage_stops: true, can_manage_orders: true,
       can_manage_pickup: true, can_manage_messages: true, can_manage_refunds: true,
@@ -122,4 +182,4 @@ function buildAdminUser(r: Record<string, unknown>): AdminUser {
     can_manage_messages: Boolean(r.can_manage_messages), can_manage_refunds: Boolean(r.can_manage_refunds),
     can_manage_users: Boolean(r.can_manage_users), can_manage_water_log: Boolean(r.can_manage_water_log),
     can_manage_reports: Boolean(r.can_manage_reports), can_manage_settings: Boolean(r.can_manage_settings) };
-}
\ No newline at end of file
+}
diff --git a/src/lib/brand-scope.ts b/src/lib/brand-scope.ts
new file mode 100644
index 0000000..e166504
--- /dev/null
+++ b/src/lib/brand-scope.ts
@@ -0,0 +1,90 @@
+/**
+ * Brand-scope helpers for multi-brand admin support.
+ *
+ * Resolution order (documented in
+ * docs/superpowers/specs/2026-06-04-multi-brand-admin-design.md):
+ *   1. URL/explicit `requested` brand id (highest priority)
+ *   2. `active_brand_id` cookie (the persistent "what brand am I in right now")
+ *   3. `adminUser.brand_id` (legacy single-brand fallback)
+ *   4. First of `adminUser.brand_ids`
+ *   5. (platform_admin only) `null` → "all brands"
+ *
+ * For non-platform-admins, the returned brand is validated against
+ * `adminUser.brand_ids` — if `requested` or the cookie brand is not in the
+ * admin's accessible brands, the resolver falls through to a brand the admin
+ * does have access to (silent recovery).
+ */
+
+import "server-only";
+import { cookies } from "next/headers";
+import type { AdminUser } from "./admin-permissions-types";
+
+export const ACTIVE_BRAND_COOKIE = "active_brand_id";
+
+/**
+ * Resolve the active brand id for the given admin user.
+ *
+ * @param adminUser - The current admin user (must already be loaded).
+ * @param requested - Optional explicit brand id (e.g. from a URL param).
+ *                    When set and the admin has access, wins over cookie.
+ * @returns The brand id to act in, or `null` for platform_admin "all brands".
+ */
+export async function getActiveBrandId(
+  adminUser: AdminUser,
+  requested?: string | null
+): Promise<string | null> {
+  const cookieStore = await cookies();
+  const cookieBrand = cookieStore.get(ACTIVE_BRAND_COOKIE)?.value ?? null;
+
+  // platform_admin: requested > cookie > null (all brands)
+  if (adminUser.role === "platform_admin") {
+    return requested ?? cookieBrand ?? null;
+  }
+
+  // Non-platform-admin: validate that requested/cookie brands are accessible
+  if (requested && adminUser.brand_ids.includes(requested)) {
+    return requested;
+  }
+  if (cookieBrand && adminUser.brand_ids.includes(cookieBrand)) {
+    return cookieBrand;
+  }
+
+  // Fall back to the legacy single brand, then first of the membership list
+  return adminUser.brand_id ?? adminUser.brand_ids[0] ?? null;
+}
+
+/**
+ * Set the persistent active-brand cookie. Should only be called after
+ * validating the admin has access (use `assertBrandAccess`).
+ */
+export async function setActiveBrandCookie(brandId: string): Promise<void> {
+  const cookieStore = await cookies();
+  cookieStore.set(ACTIVE_BRAND_COOKIE, brandId, {
+    httpOnly: true,
+    sameSite: "lax",
+    path: "/",
+    maxAge: 60 * 60 * 24 * 30, // 30 days
+  });
+}
+
+/**
+ * Clear the active-brand cookie. Used when platform_admin selects
+ * "All brands" (the cookie absence = "no specific brand pinned").
+ */
+export async function clearActiveBrandCookie(): Promise<void> {
+  const cookieStore = await cookies();
+  cookieStore.delete(ACTIVE_BRAND_COOKIE);
+}
+
+/**
+ * Throws if the admin user is not a platform_admin and does not have the
+ * given brand in their membership list. Use this for server actions and
+ * API routes that receive a brandId from URL/form/RPC return rather than
+ * `getActiveBrandId`.
+ */
+export function assertBrandAccess(adminUser: AdminUser, brandId: string): void {
+  if (adminUser.role === "platform_admin") return;
+  if (!adminUser.brand_ids.includes(brandId)) {
+    throw new Error("Brand access denied");
+  }
+}
diff --git a/supabase/migrations/207_multi_brand_admin.sql b/supabase/migrations/207_multi_brand_admin.sql
new file mode 100644
index 0000000..4719139
--- /dev/null
+++ b/supabase/migrations/207_multi_brand_admin.sql
@@ -0,0 +1,185 @@
+-- Migration 207: Multi-Brand Admin Support
+--
+-- Adds:
+--   1. New role: 'multi_brand_admin' (functionally equivalent to brand_admin,
+--      but disambiguates intent: "manages 2+ brands" vs "manages 1 brand").
+--   2. Junction table: admin_user_brands — replaces the single brand_id
+--      implicit invariant. The legacy admin_users.brand_id column is kept
+--      for backwards compatibility (see migration 220_*.sql to drop it later).
+--   3. RPCs: add_admin_user_brand / remove_admin_user_brand (manages the
+--      junction and auto-promotes/demotes the role based on brand count).
+--
+-- Design:
+--   - Composite PK (admin_user_id, brand_id) enforces uniqueness.
+--   - Index on brand_id makes "which admins are in Brand X?" queries fast.
+--   - ON DELETE CASCADE for both FKs — deleting an admin or brand cleans up.
+--   - added_by is nullable so first-insert rows (admin with no other admin)
+--     can still insert their own membership.
+
+-- ═══════════════════════════════════════════════════════════════════════════
+-- 1. Update role CHECK constraint to include multi_brand_admin
+-- ═══════════════════════════════════════════════════════════════════════════
+-- The constraint name in Supabase's auto-generated schema is conventionally
+-- "admin_users_role_check" (the default Postgres naming), but we drop both
+-- the canonical and a common alternative to be safe across schema generations.
+
+ALTER TABLE public.admin_users DROP CONSTRAINT IF EXISTS admin_users_role_check;
+ALTER TABLE public.admin_users DROP CONSTRAINT IF EXISTS admin_users_role_chk;
+
+ALTER TABLE public.admin_users
+  ADD CONSTRAINT admin_users_role_check
+  CHECK (role IN ('platform_admin', 'brand_admin', 'multi_brand_admin', 'store_employee', 'staff'));
+
+-- ═══════════════════════════════════════════════════════════════════════════
+-- 2. Create admin_user_brands junction table
+-- ═══════════════════════════════════════════════════════════════════════════
+
+CREATE TABLE IF NOT EXISTS public.admin_user_brands (
+  admin_user_id UUID NOT NULL REFERENCES public.admin_users(id) ON DELETE CASCADE,
+  brand_id      UUID NOT NULL REFERENCES public.brands(id)     ON DELETE CASCADE,
+  added_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  added_by      UUID REFERENCES public.admin_users(id),
+  PRIMARY KEY (admin_user_id, brand_id)
+);
+
+CREATE INDEX IF NOT EXISTS admin_user_brands_brand_id_idx
+  ON public.admin_user_brands(brand_id);
+
+-- ═══════════════════════════════════════════════════════════════════════════
+-- 3. Backfill: copy legacy single-brand admins into the junction
+-- ═══════════════════════════════════════════════════════════════════════════
+
+INSERT INTO public.admin_user_brands (admin_user_id, brand_id)
+SELECT id, brand_id FROM public.admin_users
+WHERE brand_id IS NOT NULL
+ON CONFLICT (admin_user_id, brand_id) DO NOTHING;
+
+-- ═══════════════════════════════════════════════════════════════════════════
+-- 4. Promote anyone with > 1 brand in the junction to multi_brand_admin
+-- ═══════════════════════════════════════════════════════════════════════════
+
+UPDATE public.admin_users
+SET role = 'multi_brand_admin'
+WHERE role = 'brand_admin'
+  AND id IN (
+    SELECT admin_user_id FROM public.admin_user_brands
+    GROUP BY admin_user_id HAVING COUNT(*) > 1
+  );
+
+-- ═══════════════════════════════════════════════════════════════════════════
+-- 5. RLS: enable on the junction (no public read; only platform_admin all)
+-- ═══════════════════════════════════════════════════════════════════════════
+
+ALTER TABLE public.admin_user_brands ENABLE ROW LEVEL SECURITY;
+
+DROP POLICY IF EXISTS "admin_user_brands_platform_admin_all" ON public.admin_user_brands;
+CREATE POLICY "admin_user_brands_platform_admin_all" ON public.admin_user_brands
+  FOR ALL TO authenticated
+  USING (
+    EXISTS (
+      SELECT 1 FROM public.admin_users au
+      WHERE au.user_id = auth.uid()
+        AND au.role = 'platform_admin'
+        AND au.active = true
+    )
+  )
+  WITH CHECK (
+    EXISTS (
+      SELECT 1 FROM public.admin_users au
+      WHERE au.user_id = auth.uid()
+        AND au.role = 'platform_admin'
+        AND au.active = true
+    )
+  );
+
+-- Brand admins can read their own membership rows (so the BrandSelector
+-- dropdown works without exposing other admins' memberships)
+DROP POLICY IF EXISTS "admin_user_brands_self_read" ON public.admin_user_brands;
+CREATE POLICY "admin_user_brands_self_read" ON public.admin_user_brands
+  FOR SELECT TO authenticated
+  USING (
+    admin_user_id IN (
+      SELECT id FROM public.admin_users
+      WHERE user_id = auth.uid() AND active = true
+    )
+  );
+
+-- ═══════════════════════════════════════════════════════════════════════════
+-- 6. RPC: add_admin_user_brand
+--    Adds an admin to a brand. Auto-promotes to multi_brand_admin if they
+--    end up with 2+ brands.
+-- ═══════════════════════════════════════════════════════════════════════════
+
+CREATE OR REPLACE FUNCTION public.add_admin_user_brand(
+  p_admin_user_id UUID,
+  p_brand_id      UUID,
+  p_added_by      UUID DEFAULT NULL
+)
+RETURNS VOID
+LANGUAGE plpgsql
+SECURITY DEFINER
+SET search_path = public
+AS $$
+BEGIN
+  INSERT INTO public.admin_user_brands (admin_user_id, brand_id, added_by)
+  VALUES (p_admin_user_id, p_brand_id, p_added_by)
+  ON CONFLICT (admin_user_id, brand_id) DO NOTHING;
+
+  -- Promote to multi_brand_admin if they now have 2+ brands
+  UPDATE public.admin_users
+  SET role = 'multi_brand_admin'
+  WHERE id = p_admin_user_id
+    AND role = 'brand_admin'
+    AND (
+      SELECT COUNT(*) FROM public.admin_user_brands
+      WHERE admin_user_id = p_admin_user_id
+    ) > 1;
+END;
+$$;
+
+-- ═══════════════════════════════════════════════════════════════════════════
+-- 7. RPC: remove_admin_user_brand
+--    Removes an admin from a brand. Auto-demotes to brand_admin if they
+--    drop to 1 brand. Does NOT demote to anything else (e.g. staff) — only
+--    brand_admin <-> multi_brand_admin transitions.
+-- ═══════════════════════════════════════════════════════════════════════════
+
+CREATE OR REPLACE FUNCTION public.remove_admin_user_brand(
+  p_admin_user_id UUID,
+  p_brand_id      UUID
+)
+RETURNS VOID
+LANGUAGE plpgsql
+SECURITY DEFINER
+SET search_path = public
+AS $$
+DECLARE
+  v_remaining_count INT;
+BEGIN
+  DELETE FROM public.admin_user_brands
+  WHERE admin_user_id = p_admin_user_id
+    AND brand_id = p_brand_id;
+
+  GET DIAGNOSTICS v_remaining_count = ROW_COUNT;
+
+  -- If we just removed a row and the user is now down to 1 brand, demote
+  IF v_remaining_count > 0 THEN
+    SELECT COUNT(*) INTO v_remaining_count
+    FROM public.admin_user_brands
+    WHERE admin_user_id = p_admin_user_id;
+
+    IF v_remaining_count = 1 THEN
+      UPDATE public.admin_users
+      SET role = 'brand_admin'
+      WHERE id = p_admin_user_id
+        AND role = 'multi_brand_admin';
+    END IF;
+  END IF;
+END;
+$$;
+
+-- ═══════════════════════════════════════════════════════════════════════════
+-- 8. Refresh PostgREST schema cache
+-- ═══════════════════════════════════════════════════════════════════════════
+
+NOTIFY pgrst, 'reload schema';