DL-084
The Server owns durable session-transcript storage: a Postgres transcript-entry store (agent_session_transcript_entries: (session_id, entry_seq) PK, UNIQUE idempotency_key, checkpoint flag, FK agent_sessions) persisted on receipt of durable TranscriptEntry frames at the CommitConversationFrame at-most-once commit seam, with CHECKPOINT SUPERSESSION server-side (the read view is latest checkpoint + later deltas — the old read-side reconstruction rule relocated to the one owner that reads). Storage backend choice and credential posture are Server-internal; the agent and Runner hold zero storage detail, zero S3 credentials
Status: Superseded by DL-093 (Matt, 2026-07-31)