deepseek-harness/packages/session-persistence-sqlite

@deepseek-ai/dsh-session-persistence-sqlite

A SQLite durable session-persistence backend — a second SessionPersistence implementation (ADR 0018), 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, crash-tail-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.

Storage model

Each SessionEvent maps 1:1 onto a row in an events table (session_id, seq, type, time, data) — data is the event payload as JSON text, so the row shape is the event verbatim (including assistant/chunk, keeping seq contiguous). Out-of-log metadata (SessionMeta) lives in a sessions row, including the mutable SessionSummary fields (updatedAt, title, firstPrompt) that update() rewrites without touching the event log. A sessions row is written only by the first append — its existence is the lazy-materialization signal (has/list report exactly the sessions that have a row), so no separate column is needed.

The repo targets Node ≥ 24 (the root engines field), which includes the stable node:sqlite module. The database opens with foreign_keys = ON (so ON DELETE CASCADE drops a session's events with its row) and journal_mode = WAL. The table-layout version is stored in PRAGMA user_version and checked on open: a fresh database is stamped with the current SCHEMA_VERSION; a database written by a newer, incompatible build (higher user_version) is rejected rather than opened against an unknown layout.

Contract semantics over rows

• Append = a transaction. append runs BEGIN/COMMIT around the batch: it runs any deferred crash-tail repair, 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.
• 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 has()/list() (which report exactly the sessions that have a row).
• Crash-tail-on-load. load() reads every stored event ordered by seq and returns only the prefix through the last complete turn/end (the SessionPersistence.load contract), computed from the seq/type columns so a malformed data in the uncommitted tail is never parsed. A batch that landed without its closing turn/end (a process killed mid-turn) is an uncommitted tail: load() stays non-mutating w.r.t. the event log and records a repair point; the next append physically DELETEs the orphaned rows inside its transaction (the one-time truncation-repair, matching the JSONL backend and the abstract contract). A seq gap inside the committed region makes the session unloadable. A session materialized by a partial first turn (all-tail, zero committed events) keeps its metadata row and stays present in has()/list() — the same as the JSONL backend, whose file likewise survives a first append that never reached turn/end.

Configuration (schemastery)

interface Config {
  path: string   // SQLite database file path, or ':memory:' for an in-process DB
}

Write path

Like the JSONL backend, the plugin also installs the session/event → buffer → session/flush drain: it snapshots each event when buffered (the live session.events object is mutable), 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.