Part of #51 (1.1.1). File-based driver: JSONL append-only event log (portable, greppable, git/rsync-friendly). duckdb is an opt-in query accelerator (SQL over JSONL) for the unread/history anti-joins — JSONL-only scans are O(n) per inbox check, so duckdb is the performance path; agmsg never installs it, it emits an AGMSG-DIRECTIVE when missing. Concurrency via flock; import/export idempotent. External driver = opt-in trust per ADR 0002. Acceptance: passes the contract test suite; duckdb-accelerated queries; clean degrade/clear error when duckdb absent.
Part of #51 (1.1.1). File-based driver: JSONL append-only event log (portable, greppable, git/rsync-friendly). duckdb is an opt-in query accelerator (SQL over JSONL) for the unread/history anti-joins — JSONL-only scans are O(n) per inbox check, so duckdb is the performance path; agmsg never installs it, it emits an AGMSG-DIRECTIVE when missing. Concurrency via flock; import/export idempotent. External driver = opt-in trust per ADR 0002. Acceptance: passes the contract test suite; duckdb-accelerated queries; clean degrade/clear error when duckdb absent.