Private
Public Access
Shows a dot on rooms with unread messages in the sidebar, updated live over WebSocket. Reuses the same offline-member audience computation already used for push notifications: a member gets the real-time signal whenever they aren't currently connected to that room's channel, which correctly covers both "room not open" and "room open but tab backgrounded" (the client leaves a room's channel while hidden). Persisted server-side via a new room_memberships.last_read_at column so state survives reload and stays consistent across devices, advanced by an explicit mark-read call the frontend makes on room-open and on each live message received while the room is genuinely visible -- gated on a live visibility check, not a cached ref, so a backgrounded-but-open room keeps accumulating unread instead of auto-marking-read the instant a message arrives somewhere it can't be seen. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>