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# ctx.sessionPersistence

`SessionPersistence` (abstract seam) — provided by `@deepseek-ai/dsh-session-persistence`.

Durable append-only session storage. Implementations preserve contiguous, losslessly JSON-serializable events; append resolves only after durability, and load balances a complete interrupted tail without rewriting committed events.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/session-persistence/session-persistence/src/index.ts#L42)

### ctx.sessionPersistence.locate(meta)

```ts website-api
/**
 * Resolve this backend's independent local artifact for a session without
 * reading, creating, flushing, or otherwise materializing it. Backends such
 * as SQLite that do not own one artifact per session return `undefined`.
 * @param meta - the immutable session header whose artifact is requested.
 * @returns the backend-specific absolute location, when one exists.
 */
abstract locate(meta: SessionHeader): SessionLocation | undefined
```

Resolve this backend's independent local artifact for a session without reading, creating, flushing, or otherwise materializing it. Backends such as SQLite that do not own one artifact per session return `undefined`.

- `meta` — the immutable session header whose artifact is requested.

**Returns** the backend-specific absolute location, when one exists.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/session-persistence/session-persistence/src/index.ts#L54)

### ctx.sessionPersistence.create(meta)

```ts website-api
/**
 * Register a new session's metadata. A backend MAY defer the physical write
 * until the first {@link append} (lazy materialization), in which case a
 * created-but-never-appended session is absent from {@link list}
 * — abandoned sessions leave nothing behind.
 * @param meta - the immutable header (id, version, cwd, lineage) to record.
 */
abstract create(meta: SessionHeader): Promise<void>
```

Register a new session's metadata. A backend MAY defer the physical write until the first append (lazy materialization), in which case a created-but-never-appended session is absent from list — abandoned sessions leave nothing behind.

- `meta` — the immutable header (id, version, cwd, lineage) to record.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/session-persistence/session-persistence/src/index.ts#L63)

### ctx.sessionPersistence.append(id, events)

```ts website-api
/**
 * Durably persist a batch of events (called from the write-behind drain at
 * the `session/flush` checkpoint). Honors the append-only and contiguous-seq
 * contracts: the first event's `seq` MUST equal the stored next-seq (after
 * `load` has durably closed any interrupted turn). Rejects non-JSON-
 * serializable `event.data` with an error naming the offending event type.
 * @param id - the session the batch belongs to.
 * @param events - the contiguous batch to persist, in seq order.
 */
abstract append(id: SessionId, events: readonly SessionEvent[]): Promise<void>
```

Durably persist a batch of events (called from the write-behind drain at the `session/flush` checkpoint). Honors the append-only and contiguous-seq contracts: the first event's `seq` MUST equal the stored next-seq (after `load` has durably closed any interrupted turn). Rejects non-JSON- serializable `event.data` with an error naming the offending event type.

- `id` — the session the batch belongs to.
- `events` — the contiguous batch to persist, in seq order.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/session-persistence/session-persistence/src/index.ts#L74)

### ctx.sessionPersistence.load(id)

```ts website-api
/**
 * Load a header and balanced contiguous log. A complete interrupted final
 * turn is preserved and durably closed with missing tool errors plus any open
 * step and turn boundaries; only a torn final record is discarded. Unknown
 * versions and corruption in the committed prefix reject.
 * @param id - the persisted session to reload.
 * @returns the header and a log ending on a balanced `turn/end`.
 */
abstract load(id: SessionId): Promise<{ meta: SessionHeader; events: SessionEvent[] }>
```

Load a header and balanced contiguous log. A complete interrupted final turn is preserved and durably closed with missing tool errors plus any open step and turn boundaries; only a torn final record is discarded. Unknown versions and corruption in the committed prefix reject.

- `id` — the persisted session to reload.

**Returns** the header and a log ending on a balanced `turn/end`.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/session-persistence/session-persistence/src/index.ts#L84)

### ctx.sessionPersistence.list()

```ts website-api
/**
 * Lightweight listing from metadata, without a full-log parse.
 * @returns one header per materialized session.
 */
abstract list(): Promise<SessionHeader[]>
```

Lightweight listing from metadata, without a full-log parse.

**Returns** one header per materialized session.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/session-persistence/session-persistence/src/index.ts#L90)
