diff --git a/app/(main)/[locale]/contacts/page.tsx b/app/(main)/[locale]/contacts/page.tsx
index 28818bd9..c8fb7a46 100644
--- a/app/(main)/[locale]/contacts/page.tsx
+++ b/app/(main)/[locale]/contacts/page.tsx
@@ -27,6 +27,7 @@ import { SidebarAppsModal } from "@/components/layout/sidebar-apps-modal";
 import { InlineAppView } from "@/components/layout/inline-app-view";
 import { useSidebarApps } from "@/hooks/use-sidebar-apps";
 import { useIsEmbedded } from "@/hooks/use-is-embedded";
+import { useProMultiAccountContacts } from "@/hooks/use-pro-multi-account-contacts";
 import { ResizeHandle } from "@/components/layout/resize-handle";
 import { useIsDesktop, useIsMobile } from "@/hooks/use-media-query";
 import { useRefreshGesture } from "@/hooks/use-refresh-gesture";
@@ -140,12 +141,18 @@ export default function ContactsPage() {
     }
   }, [initialCheckDone, isAuthenticated, authLoading]);
 
+  // Pro shell only: aggregate contacts and address books from every
+  // connected account so the sidebar lists them all. The hook is a no-op
+  // outside the embedded shell.
+  const { enabled: multiAccountEnabled, accountClients } = useProMultiAccountContacts();
+
   useEffect(() => {
+    if (isEmbedded) return;
     if (client && supportsSync && !hasFetched.current) {
       hasFetched.current = true;
       fetchContacts(client);
     }
-  }, [client, supportsSync, fetchContacts]);
+  }, [client, supportsSync, fetchContacts, isEmbedded]);
 
   // Intercept browser refresh gestures (F5, Ctrl/Cmd+R, pull-to-refresh)
   // and refresh contacts via JMAP instead of reloading the page.
@@ -153,6 +160,17 @@ export default function ContactsPage() {
     enabled: isAuthenticated && !!client && supportsSync,
     onRefresh: async () => {
       if (!client) return;
+      if (multiAccountEnabled && accountClients.length > 0) {
+        const activeId = useAuthStore.getState().activeAccountId;
+        if (activeId) {
+          const { fetchAllAccountsContacts, fetchAllAccountsAddressBooks } = useContactStore.getState();
+          await Promise.all([
+            fetchAllAccountsAddressBooks(accountClients, activeId),
+            fetchAllAccountsContacts(accountClients, activeId),
+          ]);
+          return;
+        }
+      }
       await fetchContacts(client);
     },
   });
@@ -759,6 +777,7 @@ export default function ContactsPage() {
                         }
                       } : undefined}
                       onRenameKeyword={(kw) => setRenamingKeyword(kw)}
+                      multiAccountMode={multiAccountEnabled && accountClients.length > 1}
                     />
                   </div>
                   {!isNarrow && (
diff --git a/components/contacts/contacts-sidebar.tsx b/components/contacts/contacts-sidebar.tsx
index 07afccf1..2403b33d 100644
--- a/components/contacts/contacts-sidebar.tsx
+++ b/components/contacts/contacts-sidebar.tsx
@@ -2,7 +2,7 @@
 
 import { useMemo, useState, useCallback, useEffect, useRef, type DragEvent } from "react";
 import { useTranslations } from "next-intl";
-import { BookUser, Users, Plus, Share2, Book, ChevronRight, ChevronDown, UserPlus, UsersRound, Upload, Tag, Pencil, Trash2, Settings } from "lucide-react";
+import { BookUser, User, Users, Plus, Share2, Book, ChevronRight, ChevronDown, UserPlus, UsersRound, Upload, Tag, Pencil, Trash2, Settings } from "lucide-react";
 import { useRouter } from "next/navigation";
 import { Button } from "@/components/ui/button";
 import { ContextMenu, ContextMenuItem, ContextMenuSeparator } from "@/components/ui/context-menu";
@@ -10,6 +10,7 @@ import { useContextMenu } from "@/hooks/use-context-menu";
 import { cn } from "@/lib/utils";
 import type { ContactCard, AddressBook } from "@/lib/jmap/types";
 import { getContactDisplayName } from "@/stores/contact-store";
+import { useAccountStore } from "@/stores/account-store";
 
 export type ContactCategory = "all" | { groupId: string } | { addressBookId: string } | { keyword: string } | "uncategorized";
 
@@ -32,6 +33,36 @@ interface ContactsSidebarProps {
   onDeleteAddressBook?: (addressBook: AddressBook) => void;
   onRenameKeyword?: (keyword: string) => void;
   className?: string;
+  /**
+   * Pro shell: render one collapsible section per connected local account
+   * (active first), each with "My Address Books" / "Shared from X"
+   * subsections. Mirrors the calendar sidebar's Pro layout.
+   */
+  multiAccountMode?: boolean;
+}
+
+type AddressBookAccountSplit = {
+  owned: AddressBook[];
+  sharedGroups: { label: string; books: AddressBook[] }[];
+};
+
+function splitAccountBooks(list: AddressBook[]): AddressBookAccountSplit {
+  const owned: AddressBook[] = [];
+  const sharedBuckets = new Map<string, { label: string; books: AddressBook[] }>();
+  for (const book of list) {
+    if (book.isShared) {
+      const key = book.accountId || book.accountName || book.id;
+      const bucket = sharedBuckets.get(key);
+      if (bucket) {
+        bucket.books.push(book);
+      } else {
+        sharedBuckets.set(key, { label: book.accountName || key, books: [book] });
+      }
+    } else {
+      owned.push(book);
+    }
+  }
+  return { owned, sharedGroups: Array.from(sharedBuckets.values()) };
 }
 
 const COLLAPSED_KEY = "contacts-sidebar-collapsed";
@@ -70,6 +101,7 @@ export function ContactsSidebar({
   onDeleteAddressBook,
   onRenameKeyword,
   className,
+  multiAccountMode,
 }: ContactsSidebarProps) {
   const t = useTranslations("contacts");
   const router = useRouter();
@@ -136,6 +168,47 @@ export function ContactsSidebar({
     return Array.from(map.values());
   }, [addressBooks]);
 
+  // Pro / multi-account grouping: each local account is its own collapsible
+  // section with owned / shared sub-buckets.
+  const localAccounts = useAccountStore((s) => s.accounts);
+  const activeLocalAccountId = useAccountStore((s) => s.activeAccountId);
+  const localAccountGroups = useMemo(() => {
+    if (!multiAccountMode) return [];
+    const byAccount = new Map<string, AddressBook[]>();
+    for (const book of addressBooks) {
+      const key = book.localAccountId || '__other__';
+      const list = byAccount.get(key) ?? [];
+      list.push(book);
+      byAccount.set(key, list);
+    }
+    const ordered: { key: string; label: string; split: AddressBookAccountSplit }[] = [];
+    if (activeLocalAccountId && byAccount.has(activeLocalAccountId)) {
+      const acct = localAccounts.find(a => a.id === activeLocalAccountId);
+      ordered.push({
+        key: activeLocalAccountId,
+        label: acct?.label || acct?.email || acct?.username || activeLocalAccountId,
+        split: splitAccountBooks(byAccount.get(activeLocalAccountId)!),
+      });
+      byAccount.delete(activeLocalAccountId);
+    }
+    for (const acct of localAccounts) {
+      if (!byAccount.has(acct.id)) continue;
+      ordered.push({
+        key: acct.id,
+        label: acct.label || acct.email || acct.username,
+        split: splitAccountBooks(byAccount.get(acct.id)!),
+      });
+      byAccount.delete(acct.id);
+    }
+    for (const [key, list] of byAccount.entries()) {
+      const fallback = key === '__other__'
+        ? t('address_books.title')
+        : list[0]?.accountName || key;
+      ordered.push({ key, label: fallback, split: splitAccountBooks(list) });
+    }
+    return ordered;
+  }, [multiAccountMode, addressBooks, localAccounts, activeLocalAccountId, t]);
+
   // Count contacts per address book
   const contactCountByBook = useMemo(() => {
     const counts: Record<string, number> = {};
@@ -257,47 +330,117 @@ export function ContactsSidebar({
           </span>
         </button>
 
-        {/* My Address Books */}
-        {personalBooks.length > 0 && (
-          <div className="mt-2">
-            <div className="flex items-center px-3 py-1 group">
-              <button
-                onClick={() => toggleSection("addressBooks")}
-                className="flex items-center gap-1 flex-1 text-left"
-              >
-                {collapsed.addressBooks ? (
-                  <ChevronRight className="w-3 h-3 text-muted-foreground" />
-                ) : (
-                  <ChevronDown className="w-3 h-3 text-muted-foreground" />
+        {/* Address Books: per-account groups in multi-account Pro mode, else the
+            classic "My Address Books" section. */}
+        {multiAccountMode && localAccountGroups.length > 0 ? (
+          localAccountGroups.map((group) => {
+            const sectionKey = `account-${group.key}`;
+            const expanded = !collapsed[sectionKey];
+            const { owned, sharedGroups } = group.split;
+            return (
+              <div key={group.key} className="mt-2">
+                <div className="flex items-center px-3 py-1 group">
+                  <button
+                    onClick={() => toggleSection(sectionKey)}
+                    className="flex items-center gap-1 flex-1 min-w-0 text-left"
+                  >
+                    {expanded ? (
+                      <ChevronDown className="w-3 h-3 text-muted-foreground" />
+                    ) : (
+                      <ChevronRight className="w-3 h-3 text-muted-foreground" />
+                    )}
+                    <User className="w-3 h-3 text-muted-foreground" />
+                    <span className="text-xs font-semibold text-foreground/90 uppercase tracking-wider truncate">
+                      {group.label}
+                    </span>
+                  </button>
+                </div>
+                {expanded && (
+                  <div className="pl-2">
+                    {owned.length > 0 && (
+                      <div className="mt-1">
+                        <div className="px-3 py-0.5 text-[10px] font-medium text-muted-foreground/80 uppercase tracking-wider">
+                          {t("address_books.title")}
+                        </div>
+                        {owned.map((book) => (
+                          <AddressBookItem
+                            key={book.id}
+                            book={book}
+                            isActive={typeof activeCategory === "object" && "addressBookId" in activeCategory && activeCategory.addressBookId === book.id}
+                            contactCount={contactCountByBook[book.id] || 0}
+                            onSelect={() => onSelectCategory({ addressBookId: book.id })}
+                            onDropContacts={onDropContacts}
+                            onContextMenu={(onRenameAddressBook || onShareAddressBook || onCreateContactInBook || onDeleteAddressBook) ? (e) => openBookContextMenu(e, book) : undefined}
+                          />
+                        ))}
+                      </div>
+                    )}
+                    {sharedGroups.map((sg) => (
+                      <div key={`${group.key}-shared-${sg.label}`} className="mt-1">
+                        <div className="px-3 py-0.5 text-[10px] font-medium text-muted-foreground/80 uppercase tracking-wider flex items-center gap-1">
+                          <Share2 className="w-3 h-3" />
+                          {sg.label}
+                        </div>
+                        {sg.books.map((book) => (
+                          <AddressBookItem
+                            key={book.id}
+                            book={book}
+                            isActive={typeof activeCategory === "object" && "addressBookId" in activeCategory && activeCategory.addressBookId === book.id}
+                            contactCount={contactCountByBook[book.id] || 0}
+                            onSelect={() => onSelectCategory({ addressBookId: book.id })}
+                            onDropContacts={onDropContacts}
+                            onContextMenu={(onRenameAddressBook || onShareAddressBook || onCreateContactInBook || onDeleteAddressBook) ? (e) => openBookContextMenu(e, book) : undefined}
+                          />
+                        ))}
+                      </div>
+                    ))}
+                  </div>
                 )}
-                <span className="text-xs font-medium text-muted-foreground uppercase tracking-wider">
-                  {t("address_books.title")}
-                </span>
-              </button>
-              <button
-                onClick={(e) => {
-                  e.stopPropagation();
-                  try { localStorage.setItem('settings-active-tab', 'contacts'); } catch { /* ignore */ }
-                  router.push('/settings');
-                }}
-                className="p-0.5 rounded opacity-0 group-hover:opacity-100 transition-opacity duration-150 hover:bg-muted"
-                title={t("address_books.manage")}
-              >
-                <Settings className="w-3 h-3 text-muted-foreground" />
-              </button>
+              </div>
+            );
+          })
+        ) : (
+          personalBooks.length > 0 && (
+            <div className="mt-2">
+              <div className="flex items-center px-3 py-1 group">
+                <button
+                  onClick={() => toggleSection("addressBooks")}
+                  className="flex items-center gap-1 flex-1 text-left"
+                >
+                  {collapsed.addressBooks ? (
+                    <ChevronRight className="w-3 h-3 text-muted-foreground" />
+                  ) : (
+                    <ChevronDown className="w-3 h-3 text-muted-foreground" />
+                  )}
+                  <span className="text-xs font-medium text-muted-foreground uppercase tracking-wider">
+                    {t("address_books.title")}
+                  </span>
+                </button>
+                <button
+                  onClick={(e) => {
+                    e.stopPropagation();
+                    try { localStorage.setItem('settings-active-tab', 'contacts'); } catch { /* ignore */ }
+                    router.push('/settings');
+                  }}
+                  className="p-0.5 rounded opacity-0 group-hover:opacity-100 transition-opacity duration-150 hover:bg-muted"
+                  title={t("address_books.manage")}
+                >
+                  <Settings className="w-3 h-3 text-muted-foreground" />
+                </button>
+              </div>
+              {!collapsed.addressBooks && personalBooks.map((book) => (
+                <AddressBookItem
+                  key={book.id}
+                  book={book}
+                  isActive={typeof activeCategory === "object" && "addressBookId" in activeCategory && activeCategory.addressBookId === book.id}
+                  contactCount={contactCountByBook[book.id] || 0}
+                  onSelect={() => onSelectCategory({ addressBookId: book.id })}
+                  onDropContacts={onDropContacts}
+                  onContextMenu={(onRenameAddressBook || onShareAddressBook || onCreateContactInBook || onDeleteAddressBook) ? (e) => openBookContextMenu(e, book) : undefined}
+                />
+              ))}
             </div>
-            {!collapsed.addressBooks && personalBooks.map((book) => (
-              <AddressBookItem
-                key={book.id}
-                book={book}
-                isActive={typeof activeCategory === "object" && "addressBookId" in activeCategory && activeCategory.addressBookId === book.id}
-                contactCount={contactCountByBook[book.id] || 0}
-                onSelect={() => onSelectCategory({ addressBookId: book.id })}
-                onDropContacts={onDropContacts}
-                onContextMenu={(onRenameAddressBook || onShareAddressBook || onCreateContactInBook || onDeleteAddressBook) ? (e) => openBookContextMenu(e, book) : undefined}
-              />
-            ))}
-          </div>
+          )
         )}
 
         {/* Groups section */}
@@ -398,8 +541,9 @@ export function ContactsSidebar({
           )}
         </div>
 
-        {/* Shared accounts with address books */}
-        {sharedBookGroups.map((group) => (
+        {/* Shared accounts with address books — only when not already split
+            into per-account groups above (multi-account Pro mode). */}
+        {!multiAccountMode && sharedBookGroups.map((group) => (
           <div key={group.accountId} className="mt-2">
             <div className="flex items-center px-3 py-1 group">
               <button
diff --git a/hooks/use-pro-multi-account-contacts.ts b/hooks/use-pro-multi-account-contacts.ts
new file mode 100644
index 00000000..8328f4e9
--- /dev/null
+++ b/hooks/use-pro-multi-account-contacts.ts
@@ -0,0 +1,48 @@
+"use client";
+
+import { useEffect, useMemo } from "react";
+import { useAccountStore } from "@/stores/account-store";
+import { useAuthStore } from "@/stores/auth-store";
+import { useContactStore, type ContactAccountClient } from "@/stores/contact-store";
+import { useSettingsStore } from "@/stores/settings-store";
+import { useIsEmbedded } from "@/hooks/use-is-embedded";
+
+/**
+ * Pro-shell counterpart to [[useProMultiAccountCalendars]] — aggregates
+ * contacts and address books from every connected JMAP account so the
+ * contacts sidebar lists them all, grouped by local account.
+ */
+export function useProMultiAccountContacts(): {
+  enabled: boolean;
+  accountClients: ContactAccountClient[];
+} {
+  const isEmbedded = useIsEmbedded();
+  const proInterface = useSettingsStore((s) => s.proInterface);
+  const accounts = useAccountStore((s) => s.accounts);
+  const activeAccountId = useAuthStore((s) => s.activeAccountId);
+  const fetchAllAccountsAddressBooks = useContactStore((s) => s.fetchAllAccountsAddressBooks);
+  const fetchAllAccountsContacts = useContactStore((s) => s.fetchAllAccountsContacts);
+
+  const enabled = proInterface || isEmbedded;
+
+  const accountClients = useMemo(() => {
+    if (!enabled) return [];
+    const getClientForAccount = useAuthStore.getState().getClientForAccount;
+    const pairs: ContactAccountClient[] = [];
+    for (const account of accounts) {
+      if (!account.isConnected) continue;
+      const client = getClientForAccount(account.id);
+      if (!client || !client.supportsContacts()) continue;
+      pairs.push({ localAccountId: account.id, client });
+    }
+    return pairs;
+  }, [enabled, accounts]);
+
+  useEffect(() => {
+    if (!enabled || !activeAccountId || accountClients.length === 0) return;
+    void fetchAllAccountsAddressBooks(accountClients, activeAccountId);
+    void fetchAllAccountsContacts(accountClients, activeAccountId);
+  }, [enabled, activeAccountId, accountClients, fetchAllAccountsAddressBooks, fetchAllAccountsContacts]);
+
+  return { enabled, accountClients };
+}
diff --git a/lib/jmap/types.ts b/lib/jmap/types.ts
index fbde2cc1..691b2f72 100644
--- a/lib/jmap/types.ts
+++ b/lib/jmap/types.ts
@@ -172,6 +172,9 @@ export interface ContactCard {
   accountId?: string;
   accountName?: string;
   isShared?: boolean;
+  // Local account-store ID — set when the Pro shell aggregates contacts
+  // from multiple connected accounts. See `Calendar.localAccountId`.
+  localAccountId?: string;
   language?: string;
   name?: ContactName;
   nicknames?: Record<string, ContactNickname>;
@@ -372,6 +375,8 @@ export interface AddressBook {
   accountId?: string;
   accountName?: string;
   isShared?: boolean;
+  // See `Calendar.localAccountId` — same purpose for address books.
+  localAccountId?: string;
 }
 
 export interface AddressBookRights {
diff --git a/stores/auth-store.ts b/stores/auth-store.ts
index 8c09f440..9e5647d5 100644
--- a/stores/auth-store.ts
+++ b/stores/auth-store.ts
@@ -3,6 +3,7 @@ import { persist } from 'zustand/middleware';
 import { JMAPClient, RateLimitError } from '@/lib/jmap/client';
 import type { IJMAPClient } from '@/lib/jmap/client-interface';
 import { useIdentityStore } from './identity-store';
+import { setClientLookup } from './client-registry';
 import { useContactStore } from './contact-store';
 import { useVacationStore } from './vacation-store';
 import { useCalendarStore } from './calendar-store';
@@ -1661,3 +1662,7 @@ export const useAuthStore = create<AuthState>()(
     }
   )
 );
+
+// Expose getClientForAccount to the calendar/contact stores via a small
+// shared registry — see [[stores/client-registry]] for rationale.
+setClientLookup((accountId) => useAuthStore.getState().getClientForAccount(accountId));
diff --git a/stores/calendar-store.ts b/stores/calendar-store.ts
index e8bb4f20..20db15e3 100644
--- a/stores/calendar-store.ts
+++ b/stores/calendar-store.ts
@@ -10,7 +10,7 @@ import { expandRecurringEvents } from '@/lib/recurrence-expansion';
 import { generateUUID } from '@/lib/utils';
 import { apiFetch } from '@/lib/browser-navigation';
 import { BIRTHDAY_CALENDAR_ID } from '@/lib/birthday-calendar';
-import { useAuthStore } from './auth-store';
+import { getClientByLocalAccountId } from './client-registry';
 
 /**
  * When the Pro shell aggregates calendars/events from every connected
@@ -19,10 +19,14 @@ import { useAuthStore } from './auth-store';
  * client (passed in by the page) could be on a different server entirely.
  * Falls back to the active client when `localAccountId` is unset or no
  * matching client is registered.
+ *
+ * Lookup goes through `client-registry` (not a direct auth-store import)
+ * to avoid a top-level cycle: auth-store already imports this module to
+ * bootstrap feature stores after login.
  */
 function resolveAccountClient<T extends IJMAPClient>(active: T, localAccountId?: string): T {
   if (!localAccountId) return active;
-  const lookup = useAuthStore.getState().getClientForAccount(localAccountId) as T | undefined;
+  const lookup = getClientByLocalAccountId(localAccountId) as T | undefined;
   return lookup ?? active;
 }
 
diff --git a/stores/client-registry.ts b/stores/client-registry.ts
new file mode 100644
index 00000000..18a245b8
--- /dev/null
+++ b/stores/client-registry.ts
@@ -0,0 +1,23 @@
+import type { IJMAPClient } from '@/lib/jmap/client-interface';
+
+/**
+ * Tiny indirection used by the calendar and contact stores to look up a
+ * JMAP client by local account ID without importing `auth-store` directly
+ * — that would form a top-level cycle (auth-store already imports the
+ * feature stores to bootstrap them after login).
+ *
+ * `auth-store` registers its `getClientForAccount` on module init via
+ * `setClientLookup`; the feature stores call `getClientByLocalAccountId`
+ * inside their mutations.
+ */
+type ClientLookup = (localAccountId: string) => IJMAPClient | undefined;
+
+let lookup: ClientLookup | null = null;
+
+export function setClientLookup(fn: ClientLookup): void {
+  lookup = fn;
+}
+
+export function getClientByLocalAccountId(localAccountId: string): IJMAPClient | undefined {
+  return lookup ? lookup(localAccountId) : undefined;
+}
diff --git a/stores/contact-store.ts b/stores/contact-store.ts
index df33ddd9..8f908f22 100644
--- a/stores/contact-store.ts
+++ b/stores/contact-store.ts
@@ -4,6 +4,82 @@ import type { ContactCard, AddressBook, AddressBookRights, ContactName } from '@
 import type { IJMAPClient } from '@/lib/jmap/client-interface';
 import { generateUUID } from '@/lib/utils';
 import { debug } from '@/lib/debug';
+import { getClientByLocalAccountId } from './client-registry';
+
+/** One connected JMAP account for contact multi-account aggregation. */
+export interface ContactAccountClient {
+  localAccountId: string;
+  client: IJMAPClient;
+}
+
+/**
+ * Prefix used to namespace contact/address-book IDs that belong to a
+ * non-active JMAP account when the Pro shell aggregates across accounts.
+ * The active account's IDs are left untouched so existing single-account
+ * code paths keep working unchanged.
+ */
+const CROSS_ACCOUNT_ID_DELIMITER = '::';
+
+function buildCrossAccountIdPrefix(localAccountId: string): string {
+  return `${localAccountId}${CROSS_ACCOUNT_ID_DELIMITER}`;
+}
+
+function prefixAddressBooksWithLocalAccount(
+  books: AddressBook[],
+  localAccountId: string,
+  isActiveAccount: boolean,
+): AddressBook[] {
+  if (isActiveAccount) {
+    return books.map((b) => ({ ...b, localAccountId }));
+  }
+  const prefix = buildCrossAccountIdPrefix(localAccountId);
+  return books.map((b) => ({
+    ...b,
+    id: `${prefix}${b.id}`,
+    localAccountId,
+  }));
+}
+
+function prefixContactsWithLocalAccount(
+  contacts: ContactCard[],
+  localAccountId: string,
+  isActiveAccount: boolean,
+): ContactCard[] {
+  if (isActiveAccount) {
+    return contacts.map((c) => ({ ...c, localAccountId }));
+  }
+  const prefix = buildCrossAccountIdPrefix(localAccountId);
+  return contacts.map((c) => ({
+    ...c,
+    id: `${prefix}${c.id}`,
+    localAccountId,
+    addressBookIds: c.addressBookIds
+      ? Object.fromEntries(
+          Object.entries(c.addressBookIds).map(([bookId, v]) => [`${prefix}${bookId}`, v]),
+        )
+      : c.addressBookIds,
+  }));
+}
+
+/**
+ * Route mutations back through the client that owns the target entity
+ * when in multi-account Pro mode. See [[useProMultiAccountContacts]].
+ *
+ * Lookup goes through `client-registry` (not a direct auth-store import)
+ * to avoid a top-level cycle: auth-store already imports this module to
+ * bootstrap feature stores after login.
+ */
+function resolveAccountClient<T extends IJMAPClient>(active: T, localAccountId?: string): T {
+  if (!localAccountId) return active;
+  const lookup = getClientByLocalAccountId(localAccountId) as T | undefined;
+  return lookup ?? active;
+}
+
+function stripLocalAccountPrefix(id: string, localAccountId?: string): string {
+  if (!localAccountId) return id;
+  const prefix = `${localAccountId}${CROSS_ACCOUNT_ID_DELIMITER}`;
+  return id.startsWith(prefix) ? id.slice(prefix.length) : id;
+}
 
 export function getContactDisplayName(contact: ContactCard): string {
   if (contact.name) {
@@ -85,6 +161,8 @@ interface ContactStore {
 
   fetchContacts: (client: IJMAPClient) => Promise<void>;
   fetchAddressBooks: (client: IJMAPClient) => Promise<void>;
+  fetchAllAccountsContacts: (accounts: ContactAccountClient[], activeLocalAccountId: string) => Promise<void>;
+  fetchAllAccountsAddressBooks: (accounts: ContactAccountClient[], activeLocalAccountId: string) => Promise<void>;
   createContact: (client: IJMAPClient, contact: Partial<ContactCard>) => Promise<void>;
   updateContact: (client: IJMAPClient, id: string, updates: Partial<ContactCard>) => Promise<void>;
   deleteContact: (client: IJMAPClient, id: string) => Promise<void>;
@@ -202,12 +280,64 @@ export const useContactStore = create<ContactStore>()(
         }
       },
 
+      fetchAllAccountsContacts: async (accounts, activeLocalAccountId) => {
+        set({ isLoading: true, error: null });
+        try {
+          const results = await Promise.all(
+            accounts.map(async ({ client, localAccountId }) => {
+              try {
+                const list = await client.getAllContacts();
+                return prefixContactsWithLocalAccount(
+                  list,
+                  localAccountId,
+                  localAccountId === activeLocalAccountId,
+                );
+              } catch (error) {
+                debug.error(`Failed to fetch contacts for account ${localAccountId}:`, error);
+                return [] as ContactCard[];
+              }
+            }),
+          );
+          set({ contacts: results.flat(), isLoading: false });
+        } catch (error) {
+          console.error('Failed to fetch all-account contacts:', error);
+          set({ error: 'Failed to fetch contacts', isLoading: false });
+        }
+      },
+
+      fetchAllAccountsAddressBooks: async (accounts, activeLocalAccountId) => {
+        try {
+          const results = await Promise.all(
+            accounts.map(async ({ client, localAccountId }) => {
+              try {
+                const list = await client.getAllAddressBooks();
+                return prefixAddressBooksWithLocalAccount(
+                  list,
+                  localAccountId,
+                  localAccountId === activeLocalAccountId,
+                );
+              } catch (error) {
+                debug.error(`Failed to fetch address books for account ${localAccountId}:`, error);
+                return [] as AddressBook[];
+              }
+            }),
+          );
+          set({ addressBooks: results.flat() });
+        } catch (error) {
+          console.error('Failed to fetch all-account address books:', error);
+          set({ error: 'Failed to fetch address books' });
+        }
+      },
+
       createContact: async (client, contact) => {
         set({ isLoading: true, error: null });
         try {
-          // Determine target account from the selected address book
+          // Determine target account from the selected address book. Also
+          // pin the local account so we route through the right server's
+          // client in multi-account Pro mode.
           let accountId = contact.isShared ? contact.accountId : undefined;
           let cleanedContact = contact;
+          let localAccountId = contact.localAccountId;
 
           // De-namespace addressBookIds if they reference a shared address book
           if (contact.addressBookIds) {
@@ -216,9 +346,12 @@ export const useContactStore = create<ContactStore>()(
             let sharedAccountId: string | undefined;
             for (const [bookId, value] of Object.entries(contact.addressBookIds)) {
               const book = books.find(b => b.id === bookId);
+              if (book?.localAccountId) localAccountId = book.localAccountId;
               if (book?.isShared && book.originalId) {
                 deNamespaced[book.originalId] = value;
                 sharedAccountId = book.accountId;
+              } else if (book?.originalId) {
+                deNamespaced[book.originalId] = value;
               } else {
                 deNamespaced[bookId] = value;
               }
@@ -231,6 +364,7 @@ export const useContactStore = create<ContactStore>()(
             }
           }
 
+          client = resolveAccountClient(client, localAccountId);
           const created = await client.createContact(cleanedContact, accountId);
           // Preserve shared account metadata
           if (contact.isShared && contact.accountId) {
@@ -255,8 +389,9 @@ export const useContactStore = create<ContactStore>()(
         set({ error: null });
         try {
           const contact = get().contacts.find(c => c.id === id);
-          const originalId = contact?.originalId || id;
+          const originalId = contact?.originalId || stripLocalAccountPrefix(id, contact?.localAccountId);
           const accountId = contact?.isShared ? contact.accountId : undefined;
+          client = resolveAccountClient(client, contact?.localAccountId);
 
           // De-namespace addressBookIds for shared contacts before sending to JMAP server
           let cleanedUpdates = updates;
@@ -288,8 +423,9 @@ export const useContactStore = create<ContactStore>()(
         set({ error: null });
         try {
           const contact = get().contacts.find(c => c.id === id);
-          const originalId = contact?.originalId || id;
+          const originalId = contact?.originalId || stripLocalAccountPrefix(id, contact?.localAccountId);
           const accountId = contact?.isShared ? contact.accountId : undefined;
+          client = resolveAccountClient(client, contact?.localAccountId);
           await client.deleteContact(originalId, accountId);
           set((state) => {
             const removedIds = new Set([id]);
@@ -659,8 +795,9 @@ export const useContactStore = create<ContactStore>()(
         const trimmed = newName.trim();
         if (!trimmed) return;
         try {
-          const originalId = addressBook.originalId || addressBook.id;
+          const originalId = addressBook.originalId || stripLocalAccountPrefix(addressBook.id, addressBook.localAccountId);
           const accountId = addressBook.isShared ? addressBook.accountId : undefined;
+          client = resolveAccountClient(client, addressBook.localAccountId);
           await client.updateAddressBook(originalId, { name: trimmed }, accountId);
           set((state) => ({
             addressBooks: state.addressBooks.map(b =>
@@ -677,8 +814,9 @@ export const useContactStore = create<ContactStore>()(
       removeAddressBook: async (client, addressBook) => {
         set({ error: null });
         try {
-          const originalId = addressBook.originalId || addressBook.id;
+          const originalId = addressBook.originalId || stripLocalAccountPrefix(addressBook.id, addressBook.localAccountId);
           const accountId = addressBook.isShared ? addressBook.accountId : undefined;
+          client = resolveAccountClient(client, addressBook.localAccountId);
           await client.deleteAddressBook(originalId, accountId);
           set((state) => ({
             addressBooks: state.addressBooks.filter(b => b.id !== addressBook.id),
@@ -694,8 +832,9 @@ export const useContactStore = create<ContactStore>()(
       shareAddressBook: async (client, addressBook, principalId, rights) => {
         set({ error: null });
         try {
-          const originalId = addressBook.originalId || addressBook.id;
+          const originalId = addressBook.originalId || stripLocalAccountPrefix(addressBook.id, addressBook.localAccountId);
           const accountId = addressBook.isShared ? addressBook.accountId : undefined;
+          client = resolveAccountClient(client, addressBook.localAccountId);
           await client.setAddressBookShare(originalId, principalId, rights, accountId);
           set((state) => ({
             addressBooks: state.addressBooks.map(b => {