diff --git a/src/components/email/CalendarInvitationBanner.tsx b/src/components/email/CalendarInvitationBanner.tsx
index 4479c36f..e4fcaca9 100644
--- a/src/components/email/CalendarInvitationBanner.tsx
+++ b/src/components/email/CalendarInvitationBanner.tsx
@@ -14,6 +14,7 @@ import { useCalendarStore } from '../../stores/calendar-store';
 import { useSettingsStore } from '../../stores/settings-store';
 import { useLocaleStore } from '../../stores/locale-store';
 import {
+  calendarInvitationKey,
   findCalendarAttachment,
   findParticipantByEmail,
   getInvitationMethod,
@@ -72,6 +73,11 @@ export function CalendarInvitationBanner({ email, jmapAccountId }: Props) {
   // Login address + identities + aliases, so invitations addressed to an
   // alias still show the RSVP buttons. Only an invitation looks the aliases up.
   const currentUserEmails = useUserCalendarAddresses(!!attachment && enabled);
+  // The invitation is loaded once per message, account and calendar part;
+  // a mark-read or star hands a new `email` for the same one.
+  const invitationKey = calendarInvitationKey(email, attachment, jmapAccountId);
+  const latest = React.useRef({ email, attachment });
+  latest.current = { email, attachment };
 
   const [state, setState] = React.useState<BannerState>('loading');
   const [event, setEvent] = React.useState<Partial<CalendarEvent> | null>(null);
@@ -87,12 +93,13 @@ export function CalendarInvitationBanner({ email, jmapAccountId }: Props) {
 
   React.useEffect(() => {
     let cancelled = false;
-    if (!attachment || !enabled) return;
+    const { email: current, attachment: part } = latest.current;
+    if (!invitationKey || !part || !enabled) return;
     setState('loading');
     setServerMatch(null);
     (async () => {
       try {
-        const events = await parseCalendarBlob(attachment.blobId, jmapAccountId);
+        const events = await parseCalendarBlob(part.blobId, jmapAccountId);
         if (cancelled) return;
         if (events.length === 0) {
           setState('error');
@@ -110,11 +117,11 @@ export function CalendarInvitationBanner({ email, jmapAccountId }: Props) {
         }
         // Explicit method (Content-Type params) first; JMAP usually strips
         // them, so fall back to the raw ICS METHOD line before guessing.
-        let detected = getInvitationMethod(parsed, { email, attachment });
+        let detected = getInvitationMethod(parsed, { email: current, attachment: part });
         if (detected === 'unknown') {
-          const raw = await fetchCalendarBlobText(attachment.blobId, jmapAccountId);
+          const raw = await fetchCalendarBlobText(part.blobId, jmapAccountId);
           if (cancelled) return;
-          detected = getInvitationMethod(parsed, { email, attachment, rawIcs: raw });
+          detected = getInvitationMethod(parsed, { email: current, attachment: part, rawIcs: raw });
         }
         setMethod(detected);
         setState('parsed');
@@ -123,7 +130,7 @@ export function CalendarInvitationBanner({ email, jmapAccountId }: Props) {
       }
     })();
     return () => { cancelled = true; };
-  }, [attachment, enabled, email, jmapAccountId]);
+  }, [invitationKey, enabled, jmapAccountId]);
 
   // Import into the account's default calendar; never into a shared calendar,
   // an iCal subscription (the next feed sync would delete the event) or a
diff --git a/src/lib/__tests__/calendar-invitation.test.ts b/src/lib/__tests__/calendar-invitation.test.ts
index a8ba1c27..ab1b65c7 100644
--- a/src/lib/__tests__/calendar-invitation.test.ts
+++ b/src/lib/__tests__/calendar-invitation.test.ts
@@ -1,6 +1,7 @@
 import { describe, it, expect } from 'vitest';
 import type { Email } from '../../api/types';
 import {
+  calendarInvitationKey,
   extractMethodFromContentType,
   extractMethodFromRawIcs,
   findCalendarAttachment,
@@ -113,3 +114,25 @@ describe('getInvitationTrustAssessment', () => {
     expect(getInvitationTrustAssessment(request, e, 'unknown').level).toBe('trusted');
   });
 });
+
+describe('calendarInvitationKey', () => {
+  const invite = {
+    id: 'e1',
+    keywords: {},
+    attachments: [{ blobId: 'b1', type: 'text/calendar', name: 'invite.ics', size: 10 }],
+  } as unknown as Email;
+
+  it('stays the same when only the keywords change', () => {
+    const read = { ...invite, keywords: { $seen: true } } as Email;
+    const key = calendarInvitationKey(invite, findCalendarAttachment(invite), 'group');
+    expect(key).toBe('group|e1|b1');
+    expect(calendarInvitationKey(read, findCalendarAttachment(read), 'group')).toBe(key);
+  });
+
+  it('differs per account and calendar part, and is null without one', () => {
+    const other = { ...invite, attachments: [{ ...invite.attachments![0], blobId: 'b2' }] } as Email;
+    expect(calendarInvitationKey(invite, findCalendarAttachment(invite))).toBe('|e1|b1');
+    expect(calendarInvitationKey(other, findCalendarAttachment(other))).toBe('|e1|b2');
+    expect(calendarInvitationKey({ id: 'e2' }, null)).toBeNull();
+  });
+});
diff --git a/src/lib/calendar-invitation.ts b/src/lib/calendar-invitation.ts
index ea3657a7..b5bdee51 100644
--- a/src/lib/calendar-invitation.ts
+++ b/src/lib/calendar-invitation.ts
@@ -250,6 +250,20 @@ export function findCalendarAttachment(
   return findCalendarBodyPart(email.textBody) || findCalendarBodyPart(email.htmlBody);
 }
 
+/**
+ * What identifies a message's invitation for loading it: the message, its
+ * account and the calendar part's blob. A keyword change (read, star) hands
+ * a new message object with the same key, and must not download and parse
+ * the .ics again. Null when the message has no calendar part.
+ */
+export function calendarInvitationKey(
+  email: Pick<Email, 'id'>,
+  attachment: Pick<Attachment, 'blobId'> | null,
+  jmapAccountId?: string,
+): string | null {
+  return attachment ? `${jmapAccountId ?? ''}|${email.id}|${attachment.blobId}` : null;
+}
+
 // ─── Authentication-Results / trust ──────────────────────
 
 export interface AuthenticationResults {