A SQLite durable session-persistence backend — a second `SessionPersistence` implementation ([session persistence](../../../.agents/notes/implemented/architecture/2026-06-14-session-persistence.md)), built to validate that the abstract seam and the shared `runPersistenceContract` suite are genuinely backend-agnostic. It satisfies the SAME contract as `dsh-session-persistence-jsonl` (append-only, contiguous-seq, lazy materialization, interrupted-turn close on load), expressed over `node:sqlite` rows instead of file bytes.
> **TODO:** this backend talks to `node:sqlite` directly. If a cordis database service (`cordis/db` / a `@cordisjs` SQL driver plugin) is adopted, route through that instead of holding a raw `DatabaseSync` here — the contract surface (`SessionPersistence`) would not change, only the storage driver.
Each `SessionEvent` maps 1:1 onto a row in an `events` table `(session_id, seq, type, time, data, source_event_seqs, surface_op)` — `data` is the event payload as JSON text, so the row shape is the event verbatim (including `assistant/chunk`, keeping `seq` contiguous). The two `TEXT` columns `source_event_seqs` and `surface_op` are nullable; they store the event's optional surface-metadata fields (see [session surface](../../../.agents/notes/implemented/architecture/2026-06-18-session-surface.md)). Out-of-log metadata (`SessionHeader`) lives in a `sessions` row. A `sessions` row is written only by the first `append` — its existence is the lazy-materialization signal (`list` reports exactly the sessions that have a row), so no separate column is needed.
The repository's Node range supports unflagged `node:sqlite`. The database enables foreign keys and uses the configured journal mode (`wal` by default; use a rollback mode where WAL shared-memory files are unsuitable). `PRAGMA user_version` stores the table-layout version; databases with any other version are rejected because this unreleased format has no migrations.
On filesystems with POSIX modes, the backend requests mode `0700` for missing directories and exclusively creates a missing database with mode `0600` before SQLite opens it; the process umask may further restrict both. New WAL, shared-memory, and persistent rollback-journal sidecars receive the database's resulting owner-only mode. Existing directories, database files, and sidecars keep their modes; filesystem setup errors other than an existing database fail initialization. These defaults prevent incidental exposure through a permissive process umask, but do not protect database confidentiality or integrity when another principal can replace the database entry in its parent directory.
- **Append = a transaction.** `append` runs `BEGIN`/`COMMIT` around the batch: it materializes the `sessions` row (if still lazy) and INSERTs every event, asserting the contiguous-seq contract first (the first event's `seq` must equal the stored next-seq). A mid-batch failure (a UNIQUE violation on a duplicated seq) rolls back entirely, so the stored log and the in-memory cursor stay consistent. (`load()` already balanced the stored log, so `append` never has to repair a crash tail.)
- **Lazy materialization.** `create()` records intent in memory only — no row is written until the first `append`. A created-but-never-appended session has no `sessions` row, so it is absent from `list()` (which reports exactly the sessions that have a row).
- **Interrupted-turn close on load.** `load()` implements the shared [crash-recovery contract](../../../.agents/notes/implemented/architecture/2026-06-14-session-persistence.md): preserve the valid interrupted turn, append its synthetic closing events in one transaction, and remove only a torn tail row. Committed parse errors or sequence gaps make the session unloadable. Because recovery mutates stored rows, the next append starts from a balanced log and accurate cursor.
Like the JSONL backend, the plugin also installs the `session/event` → buffer → `session/flush` drain: it copies each already-frozen event into a persistence-owned buffer, persists a fork's seed once on `session/created`, keeps a per-session write cursor so a resumed session never re-appends stored events, and seeds existing live sessions on apply (HMR does not replay `session/created`). Dispose awaits every in-flight init + final drain and then closes the database, so no write lands after teardown.
SQLite storage contributes no live prompt or schema. Loading restores the same surface history as JSONL and preserves prior headers for reconstruction; the new loop composes its current envelope. Each unanswered call in interrupted rows is balanced with the exact error text `Tool call interrupted by a crash; no result was recorded.` Row metadata and raw chunks are not messages.
Zero live-request tokens. Resume restores retained history and pays the current envelope, plus the quoted repair result for each interrupted call.
#### KV Cache effect
SQLite storage does not mutate live request prefixes. A resumed loop can reuse provider cache only when its reconstructed history, current envelope, and model route match; crash-repair results append.
- **`DatabaseSync` is synchronous** — every append transaction blocks the event loop for its duration; acceptable for local stores, a throughput ceiling for busy multi-session servers.
- **Write contention has no wait or retry policy** — the backend sets no busy timeout and retries no locked-database error, so another connection holding a write transaction makes the operation reject immediately.
- **Only the current `SCHEMA_VERSION` opens** — a database with any other schema version is rejected rather than migrated (unreleased software; no persisted user data to preserve).
- **Nothing deletes stored sessions** — rows accumulate until removed externally (the seam has no deletion surface; `ON DELETE CASCADE` is wired for such out-of-band cleanup).
