fix(dm): purge DMs with zero live members (exclude-uid, scoped) so dead-both threads clean up (S2)

packages/server/src/utils/userDeletion.dmMembership.test.ts

@@ -56,4 +56,19 @@ describe('tombstoneUser — DM membership partition', () => {
     // Survivor's 1-on-1 channel still exists and still has the survivor
     expect(testDb.select().from(schema.dmChannels).where(eq(schema.dmChannels.id, 'dm_1on1')).get()).toBeTruthy();
   });
+
+  it('keeps a Deleted<->Survivor 1-on-1, purges a Deleted<->Deleted 1-on-1', async () => {
+    const { tombstoneUser } = await import('./userDeletion.js');
+    seedUser('alreadyDead', { isDeleted: 1 });
+    seedUser('victim'); seedUser('survivor');
+    // Survivor thread — must survive
+    seedDm('dm_live', null); seedMember('dm_live', 'victim'); seedMember('dm_live', 'survivor');
+    // Both-dead thread — victim + an already-deleted partner → must be purged
+    seedDm('dm_dead', null); seedMember('dm_dead', 'victim'); seedMember('dm_dead', 'alreadyDead');
+
+    tombstoneUser('victim', { purgeContent: false });
+
+    expect(testDb.select().from(schema.dmChannels).where(eq(schema.dmChannels.id, 'dm_live')).get()).toBeTruthy();
+    expect(testDb.select().from(schema.dmChannels).where(eq(schema.dmChannels.id, 'dm_dead')).get()).toBeUndefined();
+  });
 });

packages/server/src/utils/userDeletion.ts

@@ -185,20 +185,24 @@ export function tombstoneUser(uid: string, options?: TombstoneOptions): string[]
       }
     }
 
-    // Clean up orphaned DM channels (zero members after our removal) — always runs,
-    // orphaned channels are unreachable garbage regardless of purge mode
-    const orphanedDmIds = tx.select({ id: schema.dmChannels.id })
-      .from(schema.dmChannels)
-      .all()
-      .filter(dc => {
-        const memberCount = tx.select({ id: schema.dmMembers.dmChannelId })
-          .from(schema.dmMembers)
-          .where(eq(schema.dmMembers.dmChannelId, dc.id))
-          .all()
-          .length;
-        return memberCount === 0;
-      })
-      .map(dc => dc.id);
+    // Purge DMs that are dead after this deletion: among the channels this user
+    // was in, those with zero LIVE members. The uid being tombstoned right now
+    // still reads isDeleted=0 (its row is updated below), so it is excluded
+    // explicitly — this keeps a Deleted<->Survivor 1-on-1 but purges a
+    // Deleted<->Deleted one. Scoped to the user's channels: only their
+    // membership changed here, so only these can newly become dead.
+    const orphanedDmIds = userDmChannelIds.filter(dmId => {
+      const liveOthers = tx.select({ userId: schema.dmMembers.userId })
+        .from(schema.dmMembers)
+        .innerJoin(schema.users, eq(schema.dmMembers.userId, schema.users.id))
+        .where(and(
+          eq(schema.dmMembers.dmChannelId, dmId),
+          eq(schema.users.isDeleted, 0),
+        ))
+        .all()
+        .filter(m => m.userId !== uid);
+      return liveOthers.length === 0;
+    });
 
     for (const dmId of orphanedDmIds) {
       const msgIds = tx.select({ id: schema.dmMessages.id })