From aed0d27320937545dc63bf92cf11e5fcb85d82a9 Mon Sep 17 00:00:00 2001
From: Linus Rath <139418639+rathlinus@users.noreply.github.com>
Date: Sun, 27 Sep 2026 18:21:24 +0200
Subject: [PATCH] fix: stop the mail list flashing a reload right after the
 page opens

---
 components/mail/mail-app.tsx     | 23 +++++++++++++++++++----
 lib/__tests__/deep-links.test.ts | 32 ++++++++++++++++++++++++++++++++
 lib/deep-links.ts                | 29 +++++++++++++++++++++++++++++
 3 files changed, 80 insertions(+), 4 deletions(-)

diff --git a/components/mail/mail-app.tsx b/components/mail/mail-app.tsx
index 286b3a8bc..df2c339f0 100644
--- a/components/mail/mail-app.tsx
+++ b/components/mail/mail-app.tsx
@@ -115,6 +115,7 @@ import {
   parseScheduledMailboxId,
   appPath,
   buildMailPath,
+  isFolderLinkOpen,
   parseMailPath,
   resolveFolderRef,
   type MailDeepLink,
@@ -1363,7 +1364,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
   // session and the mailbox list are up. Runs at most once per mount: after
   // this, the URL is an output of the view (see buildMailUrl), not an input.
   const deepLinkHandledRef = useRef(false);
-  const applyMailDeepLink = async (link: MailDeepLink) => {
+  const applyMailDeepLink = async (link: MailDeepLink, opts?: { onLoad?: boolean }) => {
     // A permalink can name the account it belongs to. Ids are only meaningful
     // within their account, so switch first - but only to a login that is
     // actually connected; we can't authenticate on someone's behalf. A push
@@ -1371,7 +1372,8 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
     const linkAccountId = link.accountId ?? (link.slot !== undefined
       ? useAccountStore.getState().accounts.find((a) => a.cookieSlot === link.slot)?.id ?? `slot:${link.slot}`
       : undefined);
-    if (linkAccountId && linkAccountId !== useAuthStore.getState().activeAccountId) {
+    const switchesAccount = !!linkAccountId && linkAccountId !== useAuthStore.getState().activeAccountId;
+    if (switchesAccount) {
       const target = useAccountStore.getState().accounts.find(
         (a) => a.id === linkAccountId && a.isConnected,
       );
@@ -1386,11 +1388,24 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
     if (!activeClient) return;
 
     if (link.kind === 'folder') {
-      const mailboxId = resolveFolderRef(link.ref, useEmailStore.getState().mailboxes);
+      const state = useEmailStore.getState();
+      const mailboxId = resolveFolderRef(link.ref, state.mailboxes);
       if (!mailboxId) {
         toast.error(t('deep_link.folder_not_found'));
         return;
       }
+      // Reloading the page lands here with the folder the boot fetch has just
+      // loaded; selecting it again re-fetched it under the loading overlay,
+      // so the list flashed right after it appeared.
+      if (opts?.onLoad && !switchesAccount && isFolderLinkOpen(mailboxId, {
+        selectedMailbox: state.selectedMailbox,
+        isUnifiedView: state.isUnifiedView,
+        isScheduledView: state.isScheduledView,
+        selectedKeyword: state.selectedKeyword,
+        hasSearch: !!state.searchQuery || !isFilterEmpty(state.searchFilters),
+      })) {
+        return;
+      }
       await handleMailboxSelect(mailboxId);
       return;
     }
@@ -1548,7 +1563,7 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
     deepLinkHandledRef.current = true;
 
     if (link) {
-      void applyMailDeepLinkRef.current(link);
+      void applyMailDeepLinkRef.current(link, { onLoad: true });
       return;
     }
 
diff --git a/lib/__tests__/deep-links.test.ts b/lib/__tests__/deep-links.test.ts
index 3b988c289..e43e269b5 100644
--- a/lib/__tests__/deep-links.test.ts
+++ b/lib/__tests__/deep-links.test.ts
@@ -2,6 +2,7 @@ import { describe, it, expect, vi, afterEach } from 'vitest';
 import {
   buildFolderRef,
   resolveFolderRef,
+  isFolderLinkOpen,
   buildMailPath,
   parseMailPath,
   buildCalendarPath,
@@ -121,6 +122,37 @@ describe('mail folder references', () => {
   });
 });
 
+describe('isFolderLinkOpen', () => {
+  const plainInbox = {
+    selectedMailbox: 'a',
+    isUnifiedView: false,
+    isScheduledView: false,
+    selectedKeyword: null,
+    hasSearch: false,
+  };
+
+  it('treats the folder the list already shows as open (page reload)', () => {
+    expect(isFolderLinkOpen(resolveFolderRef('inbox', MAILBOXES)!, plainInbox)).toBe(true);
+  });
+
+  it('does not treat another folder as open', () => {
+    expect(isFolderLinkOpen('b', plainInbox)).toBe(false);
+  });
+
+  it('does not treat the folder as open while a tag, search or special view covers it', () => {
+    expect(isFolderLinkOpen('a', { ...plainInbox, selectedKeyword: 'work' })).toBe(false);
+    expect(isFolderLinkOpen('a', { ...plainInbox, hasSearch: true })).toBe(false);
+    expect(isFolderLinkOpen('a', { ...plainInbox, isUnifiedView: true })).toBe(false);
+    expect(isFolderLinkOpen('a', { ...plainInbox, isScheduledView: true })).toBe(false);
+  });
+
+  it('never treats a virtual view as open - the boot fetch does not load them', () => {
+    for (const id of [UNIFIED_MAILBOX_IDS.inbox, CROSS_VIEW_IDS.unread, SCHEDULED_MAILBOX_ID]) {
+      expect(isFolderLinkOpen(id, { ...plainInbox, selectedMailbox: id })).toBe(false);
+    }
+  });
+});
+
 describe('mail paths', () => {
   it('round-trips folder, message and thread links', () => {
     const folder = buildMailPath({ mailboxId: 'c', emailId: null, threadId: null }, MAILBOXES);
diff --git a/lib/deep-links.ts b/lib/deep-links.ts
index 5ced1dfc1..d20ff3823 100644
--- a/lib/deep-links.ts
+++ b/lib/deep-links.ts
@@ -190,6 +190,35 @@ export function resolveFolderRef(ref: string, mailboxes: Mailbox[] = []): string
   return decoded || null;
 }
 
+/** The parts of the mail list's state that decide what a folder link shows. */
+export interface OpenFolderView {
+  selectedMailbox: string;
+  isUnifiedView: boolean;
+  isScheduledView: boolean;
+  selectedKeyword: string | null;
+  hasSearch: boolean;
+}
+
+/**
+ * Whether a folder link names the plain folder the list already shows.
+ *
+ * The address bar carries the open folder (`buildMailPath`), so reloading the
+ * page hands that folder back as a link once the boot fetch has loaded it.
+ * Selecting it again would only fetch the same list a second time under the
+ * loading overlay. Virtual views are never "already open" at boot: the boot
+ * fetch does not load them.
+ */
+export function isFolderLinkOpen(mailboxId: string, view: OpenFolderView): boolean {
+  if (VIRTUAL_ALIAS_BY_ID[mailboxId]) return false;
+  return (
+    mailboxId === view.selectedMailbox &&
+    !view.isUnifiedView &&
+    !view.isScheduledView &&
+    !view.selectedKeyword &&
+    !view.hasSearch
+  );
+}
+
 /**
  * The canonical path for the current mail view. Returns `/mail` for the bare
  * list so the address bar stays clean when nothing is open.