From 36160f9fbdda59efc3e6597f0c8ede792c32569e Mon Sep 17 00:00:00 2001
From: Linus Rath <139418639+rathlinus@users.noreply.github.com>
Date: Sun, 1 Nov 2026 06:00:43 +0100
Subject: [PATCH] fix: answer for a group mailbox as the group when the group
 address is one of your identities #634

---
 lib/__tests__/calendar-delegate.test.ts |  7 +++++++
 lib/calendar-delegate.ts                | 14 +++++++++-----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/lib/__tests__/calendar-delegate.test.ts b/lib/__tests__/calendar-delegate.test.ts
index 8f3e27de1..aea6584e0 100644
--- a/lib/__tests__/calendar-delegate.test.ts
+++ b/lib/__tests__/calendar-delegate.test.ts
@@ -45,6 +45,13 @@ describe('resolveAnswerTargets', () => {
     expect(view.targets[0].sentBy).toBeUndefined();
   });
 
+  it('answers as the group also when the member has the group address as an identity', () => {
+    const view = resolveAnswerTargets(base(invitation(['team@example.org'], { accountId: 'team' }), {
+      owner: TEAM, userEmails: ['bob@example.org', 'team@example.org'], canRsvpSelf: true,
+    }));
+    expect(view.targets.map((t) => [t.kind, t.participantId, t.sentBy])).toEqual([['owner', 'team', undefined]]);
+  });
+
   it('offers no answer for the owner without edit access, and says why', () => {
     for (const rights of [CALENDAR_PRESETS.read, { ...CALENDAR_PRESETS.read, mayRSVP: true }]) {
       const view = resolveAnswerTargets(base(invitation(['alice@example.org']), { calendar: { isShared: true, myRights: rights } }));
diff --git a/lib/calendar-delegate.ts b/lib/calendar-delegate.ts
index 5aa8555e9..04f63083e 100644
--- a/lib/calendar-delegate.ts
+++ b/lib/calendar-delegate.ts
@@ -99,27 +99,31 @@ export function resolveAnswerTargets(input: ResolveAnswerInput): AnswerView {
 
   if (calendar?.isShared && owner) {
     const ownerId = getUserParticipantId(event, owner.emails);
-    if (ownerId && ownerId !== selfId && !isOrganizer(event, owner.emails) && !eventHasNoOwner(event)) {
-      const participant = event.participants![ownerId];
+    // Members of a group often have the group's address as an identity of
+    // their own: the group's participant is still answered as the group.
+    const ownersOwn = ownerId && (ownerId !== selfId || owner.isGroup);
+    if (ownersOwn && !isOrganizer(event, owner.emails) && !eventHasNoOwner(event)) {
+      const participant = event.participants![ownerId!];
       const answeredBy = addressOf(participant.sentBy);
       if (!calendar.myRights?.mayWriteAll) {
         return { targets: selfTarget(), note: { kind: 'no_write', owner: owner.name }, answeredBy };
       }
-      if (input.server016 && selfId) {
+      const alsoInvited = !!selfId && selfId !== ownerId;
+      if (input.server016 && alsoInvited) {
         return { targets: ownCopyTarget(), note: { kind: 'also_invited', owner: owner.name }, answeredBy };
       }
       const delegate = userEmails[0]?.trim().toLowerCase();
       const ownerTarget: AnswerTarget = {
         kind: 'owner',
         eventId: event.id,
-        participantId: ownerId,
+        participantId: ownerId!,
         status: participant.participationStatus ?? null,
         ownerName: owner.name,
         // Always the mailto: form: Stalwart passes sentBy through unchecked,
         // and RFC 5545's SENT-BY needs a cal-address.
         ...(!owner.isGroup && delegate ? { sentBy: `mailto:${delegate}` } : {}),
       };
-      return { targets: [ownerTarget, ...(selfId ? ownCopyTarget() : [])], note: null, answeredBy };
+      return { targets: [ownerTarget, ...(alsoInvited ? ownCopyTarget() : [])], note: null, answeredBy };
     }
   }