fix: prevent loading flash when switching to a cached account

app/(main)/[locale]/page.tsx

@@ -980,11 +980,16 @@ export default function Home() {
 
         await refreshScheduledMetadata(client);
 
-        // Fetch emails for the selected mailbox after scheduled metadata is available.
+        // Fetch emails for the selected mailbox after scheduled metadata is
+        // available. If the list is already populated (an account switch
+        // restored a cached snapshot, or login prefetched it), refresh in the
+        // background so the visible mail doesn't flash a loading overlay; only
+        // a genuine empty first load shows the skeleton.
+        const background = state.emails.length > 0;
         if (selectedMailboxId) {
-          await fetchEmails(client, selectedMailboxId);
+          await fetchEmails(client, selectedMailboxId, { background });
         } else {
-          await fetchEmails(client);
+          await fetchEmails(client, undefined, { background });
         }
 
         fetchTagCounts(client);

stores/email-store.ts

@@ -148,7 +148,7 @@ interface EmailStore {
 
   // JMAP operations
   fetchMailboxes: (client: IJMAPClient) => Promise<void>;
-  fetchEmails: (client: IJMAPClient, mailboxId?: string) => Promise<void>;
+  fetchEmails: (client: IJMAPClient, mailboxId?: string, opts?: { background?: boolean }) => Promise<void>;
   // Eager post-login bootstrap: fires mailboxes/quota/emails so the round-trips
   // overlap with Next's soft-nav + home-page hydration. Safe to call multiple
   // times; later calls are no-ops while a prior one is in flight.
@@ -1035,8 +1035,12 @@ export const useEmailStore = create<EmailStore>((set, get) => ({
     return target.__prefetchPromise;
   },
 
-  fetchEmails: async (client, mailboxId) => {
+  fetchEmails: async (client, mailboxId, opts) => {
-    set({ isLoading: true, error: null }); // Keep previous emails visible during transition
+    // A background refresh (e.g. after an account switch restored a cached list)
+    // repopulates the list without showing the loading overlay, so switching to
+    // an already-visited account doesn't flash a spinner over the visible mail.
+    const background = opts?.background ?? false;
+    set(background ? { error: null } : { isLoading: true, error: null }); // Keep previous emails visible during transition
     try {
       const targetMailboxId = mailboxId || get().selectedMailbox;
       if (targetMailboxId === VIRTUAL_SCHEDULED_MAILBOX_ID) {
@@ -1093,13 +1097,19 @@ export const useEmailStore = create<EmailStore>((set, get) => ({
       void get().fetchThreadEmailCounts(client);
     } catch (error) {
       console.error('Failed to fetch emails:', error);
-      set({
+      // A failed background refresh must not wipe the list it was refreshing -
-        error: error instanceof Error ? error.message : "Failed to fetch emails",
+      // keep the restored/prefetched emails visible and just surface the error.
-        isLoading: false,
+      if (background) {
-        emails: [],
+        set({ error: error instanceof Error ? error.message : "Failed to fetch emails" });
-        hasMoreEmails: false,
+      } else {
-        totalEmails: 0
+        set({
-      });
+          error: error instanceof Error ? error.message : "Failed to fetch emails",
+          isLoading: false,
+          emails: [],
+          hasMoreEmails: false,
+          totalEmails: 0
+        });
+      }
     }
   },