Matrix is the record and the mouth its only reader: the tail is assembled from the deliveries and contexts the mouth already sends (no new endpoint, no stored copy). Newest 60 lines / 24 KiB, oldest dropped with a marker; public sessions read the rooms she may speak in, a DM session its own room alone; a first poll that fails degrades to a tail-unavailable note instead of failing the wake.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>