The ReplacingMergeTree bug was a genuine production hazard: under certain lazy-FINAL optimization paths the engine silently lost the is_deleted column from the output header and aborted the server. Anyone relying on deduplication with soft deletes should treat this as a must-upgrade. The release also ships two smaller additions — independent subquery-level query caching via `use_query_cache = true`, and an experimental browser-based web terminal at `/webterminal` (disabled by default, WebSocket-backed). The terminal is a nice dev convenience but nothing to enable on an exposed instance without understanding the access model.