diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1fac777..794c51a4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,28 @@
 # Changelog
 
+## 1.6.1 (2026-05-04)
+
+### Features
+
+- **Updates**: Update-available detection with non-dismissible notice and dev-reload refresh
+- **Plugins**: New plugin hooks for compose, attachments, search, lifecycle, and routing
+- **Sharing**: Share indicators for calendars and contacts, updated JMAP capabilities (#244)
+- **Mail**: Auto-add recipients to trusted senders when replying
+- **Identity**: Sanitize identity display name to prevent invalid `From` headers
+
+### Fixes
+
+- **Mobile**: Synchronize mobile submenu view with browser history for better navigation
+- **Viewer**: Update email viewer styles to improve overflow handling
+- **Auth**: Ensure `cookieSlot` consistency during account updates in auth store
+- **Auth**: Thread per-account cookie slot through OAuth flows
+- **Calendar**: Square the colored left marker on calendar events
+- **About**: Show git commit in About instead of "unknown"
+
+### i18n
+
+- Update mailbox context menu translations across 12 locales
+
 ## 1.6.0 (2026-05-01)
 
 ### Features
diff --git a/README.md b/README.md
index 964c9e72..0694d9a8 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@ A modern, self-hosted webmail client for [Stalwart Mail Server](https://stalw.ar
 
 [![License: AGPL v3](https://img.shields.io/badge/license-AGPL%20v3-blue.svg?logo=gnu&logoColor=white)](LICENSE)
 [![Discord](https://img.shields.io/discord/1482128142939455674?color=7289da&label=discord&logo=discord&logoColor=white)](https://discord.gg/tYCujymGrT)
-[![Version](https://img.shields.io/badge/version-1.6.0-green.svg?logo=git&logoColor=white)](CHANGELOG.md)
+[![Version](https://img.shields.io/badge/version-1.6.1-green.svg?logo=git&logoColor=white)](CHANGELOG.md)
 [![Docker](https://img.shields.io/badge/docker-ghcr.io%2Fbulwarkmail%2Fwebmail-blue?logo=docker&logoColor=white)](https://ghcr.io/bulwarkmail/webmail)
 
 </div>
diff --git a/VERSION b/VERSION
index ce6a70b9..2eda823f 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.6.0
\ No newline at end of file
+1.6.1
\ No newline at end of file
diff --git a/app/[locale]/login/page.tsx b/app/[locale]/login/page.tsx
index 8e0872cb..5bdd1938 100644
--- a/app/[locale]/login/page.tsx
+++ b/app/[locale]/login/page.tsx
@@ -7,6 +7,7 @@ import { useTranslations } from "next-intl";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import { useAuthStore } from "@/stores/auth-store";
+import { useAccountStore } from "@/stores/account-store";
 import { useThemeStore } from "@/stores/theme-store";
 import { useShallow } from "zustand/react/shallow";
 import { useConfig } from "@/hooks/use-config";
@@ -460,6 +461,16 @@ export default function LoginPage() {
       sessionStorage.setItem("oauth_add_account_mode", "true");
     }
 
+    // Persist the next-free cookie slot so loginWithOAuth (in stores/auth-store.ts)
+    // writes the refresh token to the correct per-account jmap_rt_<slot> cookie.
+    // loginWithOAuth reads this key but it was previously never written, so every
+    // OAuth account collapsed onto slot 0 and clobbered earlier accounts' refresh
+    // tokens. getNextCookieSlot() returns 0 when no accounts exist (correct for
+    // first sign-in) and the lowest unused slot otherwise (correct for "+ Add
+    // Account").
+    const nextSlot = useAccountStore.getState().getNextCookieSlot();
+    sessionStorage.setItem("oauth_cookie_slot", nextSlot.toString());
+
     const authUrl = new URL(oauthMetadata.authorization_endpoint);
     authUrl.searchParams.set("response_type", "code");
     authUrl.searchParams.set("client_id", oauthClientId);
diff --git a/app/[locale]/settings/page.tsx b/app/[locale]/settings/page.tsx
index eeda92b8..543c3b24 100644
--- a/app/[locale]/settings/page.tsx
+++ b/app/[locale]/settings/page.tsx
@@ -213,6 +213,22 @@ export default function SettingsPage() {
     }
   }, [initialCheckDone, isAuthenticated, authLoading]);
 
+  // Sync the mobile submenu view with browser history so the system back
+  // button (or gesture) returns to the settings list before exiting /settings.
+  useEffect(() => {
+    if (isDesktop) return;
+    if (typeof window === 'undefined') return;
+    if (!mobileShowContent) return;
+
+    window.history.pushState({ __settingsSubmenu: true }, '');
+
+    const handlePop = () => {
+      setMobileShowContent(false);
+    };
+    window.addEventListener('popstate', handlePop);
+    return () => window.removeEventListener('popstate', handlePop);
+  }, [isDesktop, mobileShowContent]);
+
   if (!isAuthenticated) {
     return null;
   }
@@ -321,7 +337,7 @@ export default function SettingsPage() {
             <Button
               variant="ghost"
               size="icon"
-              onClick={() => setMobileShowContent(false)}
+              onClick={() => window.history.back()}
               className="h-10 w-10"
             >
               <ArrowLeft className="w-5 h-5" />
diff --git a/app/api/auth/sso/complete/route.ts b/app/api/auth/sso/complete/route.ts
index fcbf6d33..eba9a7b7 100644
--- a/app/api/auth/sso/complete/route.ts
+++ b/app/api/auth/sso/complete/route.ts
@@ -13,12 +13,18 @@ export async function POST(request: NextRequest) {
   const cookieStore = await cookies();
 
   try {
-    const { code, state } = await request.json();
+    const { code, state, slot: bodySlot } = await request.json();
 
     if (!code || !state) {
       return NextResponse.json({ error: 'Missing code or state' }, { status: 400 });
     }
 
+    // Per-account refresh-token cookie slot. Without this the route hardcoded
+    // slot 0, so the "+ Add Account" flow overwrote the first account's
+    // refresh-token cookie. Default to 0 for back-compat with any caller that
+    // omits slot. Mirrors the validation in /api/auth/token POST.
+    const slot = typeof bodySlot === 'number' && bodySlot >= 0 && bodySlot <= 4 ? bodySlot : 0;
+
     // Read and decrypt the pending SSO cookie
     const pendingCookie = cookieStore.get(SSO_PENDING_COOKIE)?.value;
     if (!pendingCookie) {
@@ -58,9 +64,9 @@ export async function POST(request: NextRequest) {
     // Exchange code for tokens
     const tokens = await exchangeCodeForTokens(code, codeVerifier, redirectUri);
 
-    // Store refresh token
+    // Store refresh token in the per-account cookie slot.
     if (tokens.refresh_token) {
-      const cookieName = refreshTokenCookieName(0);
+      const cookieName = refreshTokenCookieName(slot);
       cookieStore.set(cookieName, tokens.refresh_token, getCookieOptions());
     }
 
diff --git a/components/email/email-viewer.tsx b/components/email/email-viewer.tsx
index 81c7ed42..f92b435a 100644
--- a/components/email/email-viewer.tsx
+++ b/components/email/email-viewer.tsx
@@ -3881,7 +3881,7 @@ export function EmailViewer({
       )}
 
       {/* Email Content Area */}
-      <div className={cn("flex-1 overflow-auto bg-muted/30", isMobile && "pb-16")}>
+      <div className={cn("flex-1 overflow-auto overscroll-contain bg-muted/30", isMobile && "pb-16")}>
 
       {/* === SENDER INFO (Desktop) === */}
       <div className="hidden lg:block bg-background border-b border-border px-6" style={{ paddingBlock: 'var(--density-header-py)' }}>
diff --git a/components/settings/share-collection-dialog.tsx b/components/settings/share-collection-dialog.tsx
index 4ef3022a..e05ea947 100644
--- a/components/settings/share-collection-dialog.tsx
+++ b/components/settings/share-collection-dialog.tsx
@@ -79,7 +79,7 @@ export function ShareCollectionDialog({
   const t = useTranslations("sharing");
   const tCommon = useTranslations("common");
   const modalRef = useRef<HTMLDivElement>(null);
-  const [principals, setPrincipals] = useState<Principal[]>([]);
+  const [allPrincipals, setAllPrincipals] = useState<Principal[]>([]);
   const [loadingPrincipals, setLoadingPrincipals] = useState(true);
   const [search, setSearch] = useState("");
   const [savingId, setSavingId] = useState<string | null>(null);
@@ -91,23 +91,28 @@ export function ShareCollectionDialog({
     setLoadingPrincipals(true);
     client.getPrincipals().then((list) => {
       if (cancelled) return;
-      // Exclude the user themselves and any principal that already has a share
-      const existing = new Set(Object.keys(shareWith || {}));
-      const filtered = list.filter((p) => p.id !== ownAccountId && !existing.has(p.id));
-      setPrincipals(filtered);
+      setAllPrincipals(list);
       setLoadingPrincipals(false);
     }).catch(() => {
       if (!cancelled) setLoadingPrincipals(false);
     });
     return () => { cancelled = true; };
-  }, [client, ownAccountId, shareWith]);
+  }, [client]);
 
-  // Map principal id -> Principal for displayed shares
+  // Map of every fetched principal by id, used for name/description lookups in
+  // the shared list. Must include principals that already have a share so the
+  // list shows their name rather than the raw id.
   const allPrincipalsById = useMemo(() => {
     const map = new Map<string, Principal>();
-    for (const p of principals) map.set(p.id, p);
+    for (const p of allPrincipals) map.set(p.id, p);
     return map;
-  }, [principals]);
+  }, [allPrincipals]);
+
+  // Principals available to add: exclude self and anyone already shared with.
+  const principals = useMemo(() => {
+    const existing = new Set(Object.keys(shareWith || {}));
+    return allPrincipals.filter((p) => p.id !== ownAccountId && !existing.has(p.id));
+  }, [allPrincipals, ownAccountId, shareWith]);
 
   // Close on Escape, focus trap, click outside
   useEffect(() => {
@@ -155,8 +160,6 @@ export function ShareCollectionDialog({
     setSavingId(principal.id);
     try {
       await onShare(principal.id, rights);
-      // Move principal out of the "to add" list
-      setPrincipals((prev) => prev.filter((p) => p.id !== principal.id));
       setShowAdd(false);
       setSearch("");
       toast.success(t("share_added"));
diff --git a/lib/jmap/client.ts b/lib/jmap/client.ts
index 3faf65dc..45d83f2a 100644
--- a/lib/jmap/client.ts
+++ b/lib/jmap/client.ts
@@ -3314,6 +3314,9 @@ export class JMAPClient implements IJMAPClient {
       const err = result.notUpdated[calendarId];
       throw new Error(err.description || "Failed to update calendar share");
     }
+    if (!result?.updated || !(calendarId in result.updated)) {
+      throw new Error("Server did not confirm the share update");
+    }
   }
 
   /**
@@ -3339,6 +3342,9 @@ export class JMAPClient implements IJMAPClient {
       const err = result.notUpdated[addressBookId];
       throw new Error(err.description || "Failed to update address book share");
     }
+    if (!result?.updated || !(addressBookId in result.updated)) {
+      throw new Error("Server did not confirm the share update");
+    }
   }
 
   private async fetchPaginatedContacts(
diff --git a/package-lock.json b/package-lock.json
index 212f7601..ad31f5b0 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "bulwark-webmail",
-  "version": "1.6.0",
+  "version": "1.6.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "bulwark-webmail",
-      "version": "1.6.0",
+      "version": "1.6.1",
       "license": "AGPL-3.0-only",
       "dependencies": {
         "@tanstack/react-virtual": "^3.13.24",
diff --git a/package.json b/package.json
index 7599ac72..ca349352 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "bulwark-webmail",
-  "version": "1.6.0",
+  "version": "1.6.1",
   "description": "Bulwark Webmail - a modern webmail client built for Stalwart Mail Server",
   "author": "Bulwark Webmail <bulwark@rbm.systems>",
   "license": "AGPL-3.0-only",
diff --git a/stores/auth-store.ts b/stores/auth-store.ts
index 008b020f..610ec4be 100644
--- a/stores/auth-store.ts
+++ b/stores/auth-store.ts
@@ -601,12 +601,21 @@ export const useAuthStore = create<AuthState>()(
         set({ isLoading: true, error: null, isRateLimited: false, rateLimitUntil: null });
 
         try {
-          // Determine slot for this account (use slot from sessionStorage if re-adding)
+          // Determine slot for this account (use slot from sessionStorage if re-adding).
+          // Note: `parseInt(getItem(...) || '0')` collapses "no value set" and
+          // "value is 0" into the same case, so the fallback to getNextCookieSlot()
+          // never fired for the common "+ Add Account" path — every OAuth account
+          // ended up on slot 0 and overwrote earlier accounts' refresh-token cookies.
+          // Distinguishing rawSlot === null from a parsed 0 fixes that. The page
+          // also writes oauth_cookie_slot before redirecting to the IdP.
           const accountStore = useAccountStore.getState();
-          const pendingSlot = typeof window !== 'undefined'
-            ? parseInt(sessionStorage.getItem('oauth_cookie_slot') || '0', 10)
-            : 0;
-          const slot = pendingSlot >= 0 && pendingSlot <= 4 ? pendingSlot : accountStore.getNextCookieSlot();
+          const rawSlot = typeof window !== 'undefined'
+            ? sessionStorage.getItem('oauth_cookie_slot')
+            : null;
+          const pendingSlot = rawSlot !== null ? parseInt(rawSlot, 10) : NaN;
+          const slot = !isNaN(pendingSlot) && pendingSlot >= 0 && pendingSlot <= 4
+            ? pendingSlot
+            : accountStore.getNextCookieSlot();
 
           const tokenRes = await apiFetch(`/api/auth/token?slot=${slot}`, {
             method: 'POST',
@@ -659,6 +668,12 @@ export const useAuthStore = create<AuthState>()(
             hasError: false,
             isDefault: accountStore.accounts.length === 0,
           });
+          // The refresh-token cookie was written to `slot`. Force the stored
+          // cookieSlot to match: addAccount preserves the prior slot when
+          // re-adding an existing account, and recomputes via getNextCookieSlot
+          // for new accounts (which may disagree if another tab claimed a slot
+          // mid-flow). Either way, the cookie's slot is the source of truth.
+          accountStore.updateAccount(accountId, { cookieSlot: slot });
           accountStore.setActiveAccount(accountId);
 
           await syncStalwartAuthContext(serverUrl, username, client.getAuthHeader(), slot);
@@ -718,12 +733,19 @@ export const useAuthStore = create<AuthState>()(
         set({ isLoading: true, error: null, isRateLimited: false, rateLimitUntil: null });
 
         try {
-          // Server-side SSO: the server holds the PKCE verifier in an encrypted cookie
+          // Server-side SSO: the server holds the PKCE verifier in an encrypted cookie.
+          // Pass the next-free cookie slot so /api/auth/sso/complete writes the refresh
+          // token to the correct per-account jmap_rt_<slot> cookie. Without this the
+          // route hardcoded slot 0, which broke "+ Add Account" by overwriting the
+          // first account's refresh-token cookie.
+          const accountStore = useAccountStore.getState();
+          const slot = accountStore.getNextCookieSlot();
+
           const ssoRes = await apiFetch('/api/auth/sso/complete', {
             method: 'POST',
             headers: { 'Content-Type': 'application/json' },
             credentials: 'include',
-            body: JSON.stringify({ code, state }),
+            body: JSON.stringify({ code, state, slot }),
           });
 
           if (!ssoRes.ok) {
@@ -741,8 +763,6 @@ export const useAuthStore = create<AuthState>()(
             throw new Error('Server URL not configured');
           }
 
-          const accountStore = useAccountStore.getState();
-
           const refreshFn = get().refreshAccessToken;
           const client = JMAPClient.withBearer(ssoServerUrl, access_token, '', () => refreshFn());
           await client.connect();
@@ -779,10 +799,13 @@ export const useAuthStore = create<AuthState>()(
             hasError: false,
             isDefault: accountStore.accounts.length === 0,
           });
+          // The refresh-token cookie was written to `slot` by /api/auth/sso/complete.
+          // Force the stored cookieSlot to match — see loginWithOAuth above for the
+          // re-add and concurrent-tab cases this guards against.
+          accountStore.updateAccount(accountId, { cookieSlot: slot });
           accountStore.setActiveAccount(accountId);
 
-          const cookieSlot = accountStore.getAccountById(accountId)?.cookieSlot ?? 0;
-          await syncStalwartAuthContext(ssoServerUrl, username, client.getAuthHeader(), cookieSlot);
+          await syncStalwartAuthContext(ssoServerUrl, username, client.getAuthHeader(), slot);
 
           set({
             isAuthenticated: true,