B1 of the Matrix protocol-gaps roadmap, gate-green (688 tests):
- StateEvent.RoomRetention + a shared utils/retention.ts (presets, isExpired,
getRoomRetentionMs) with tests.
- RoomRetention settings control (PL-gated preset buttons Off/1d/1w/1m) in Room
Settings → General → Message Retention.
- Timeline hides events past the room's max_lifetime (gated behind Show Hidden
Events, like redactions) — messages visually disappear, losslessly.
- Opt-in setting enforceRetentionLocally (default OFF) + a headless
RetentionSweeper that permanently redacts the user's OWN expired messages
(own-only, loaded-timeline scope, dedupe + retry). Nothing auto-deletes unless
the user opts in.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
