diff --git a/HellionChat/MessageStore.cs b/HellionChat/MessageStore.cs
index c46f841..b77701e 100644
--- a/HellionChat/MessageStore.cs
+++ b/HellionChat/MessageStore.cs
@@ -464,11 +464,35 @@ internal class MessageStore : IDisposable
         cmd.ExecuteNonQuery();
     }
 
+    // Drops the full-text index and marks it for a rebuild.
+    //
+    // messages_fts stores sender_text and content_text in the clear, and no
+    // delete path touched it: ClearMessages, CleanupRetainOnly and the retention
+    // sweep all removed rows from `messages` only. The plain text of every
+    // "deleted" message stayed on disk.
+    //
+    // Worse, it was self-sealing. InitFtsReadyCache treats a non-empty index as
+    // ready, so after a wipe the index stayed full, the readiness flag stayed
+    // true, and the rebuild that would have cleared it never ran again.
+    //
+    // Wiping rather than deleting matched rows: message_guid is stored as a GUID
+    // string while messages.Id is a BLOB, so the two cannot be joined in SQL.
+    // The index is derived data and rebuilds from the surviving rows on the next
+    // start, which is the cheap and provably complete option.
+    //
+    // Caller must already hold _readLock.
+    private void InvalidateFtsIndex()
+    {
+        Connection.Execute("DELETE FROM messages_fts;");
+        _ftsReady = false;
+    }
+
     internal void ClearMessages()
     {
         lock (_readLock)
         {
             Connection.Execute("DELETE FROM messages;");
+            InvalidateFtsIndex();
             PerformMaintenance();
         }
     }
@@ -568,7 +592,11 @@ internal class MessageStore : IDisposable
             }
 
             if (deleted > 0)
+            {
+                InvalidateFtsIndex();
                 PerformMaintenance();
+            }
+
             return deleted;
         }
     }
@@ -592,7 +620,16 @@ internal class MessageStore : IDisposable
                 cmd.CommandTimeout = 600;
                 deleted = cmd.ExecuteNonQuery();
             }
-            PerformMaintenance();
+
+            // Skipped when nothing matched: VACUUM rewrites the whole file, and
+            // running it for zero deleted rows costs seconds on a large database
+            // for no benefit. DeleteByRetentionPolicy already guards this way.
+            if (deleted > 0)
+            {
+                InvalidateFtsIndex();
+                PerformMaintenance();
+            }
+
             return deleted;
         }
     }