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# ctx.sessions

`SessionStore` — provided by `@deepseek-ai/dsh-session`.

In-memory session store (`ctx.sessions`).
Persistence is intentionally not implemented here — persistence plugins subscribe to `session/event` and flush on `session/flush` / dispose.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/core/session/src/index.ts#L577)

### ctx.sessions.create(id?, options?)

```ts website-api
/**
 * Create a session owned by the calling fiber: disposing that fiber stops
 * event notification and removes the session from the store. `options.seed`
 * populates the session with a copy of those events (replay/fork);
 * `options.meta` attaches creation metadata (validated absolute `cwd`,
 * `parentSession` lineage) as the immutable {@link SessionHeader} (the store
 * fills `version`/`id`/`createdAt`).
 *
 * For an agent whose session must be torn down IN ORDER with its loop (so the
 * loop's final flush is captured before the store attachment ends), do NOT use this
 * — fold the session lifecycle into the agent's own effect via
 * {@link prepare} + {@link enter} + {@link announce} (see
 * `dsh-agent-loop`'s creation transaction).
 *
 * @param id - the session id; omitted, the store mints `session-<n>`.
 * @param options - seed events and/or creation metadata for the header.
 * @returns the live session, already entered and announced.
 * @throws if a session with `id` already exists, metadata is not a plain
 *   lossless-JSON record with valid scalar fields, or `meta.cwd` is a
 *   non-absolute path (storage backends key directories off it).
 */
create(id?: SessionId, options?: CreateSessionOptions): Session
```

Create a session owned by the calling fiber: disposing that fiber stops event notification and removes the session from the store. `options.seed` populates the session with a copy of those events (replay/fork); `options.meta` attaches creation metadata (validated absolute `cwd`, `parentSession` lineage) as the immutable SessionHeader (the store fills `version`/`id`/`createdAt`).
For an agent whose session must be torn down IN ORDER with its loop (so the loop's final flush is captured before the store attachment ends), do NOT use this — fold the session lifecycle into the agent's own effect via prepare + enter + announce (see `dsh-agent-loop`'s creation transaction).

- `id` — the session id; omitted, the store mints `session-<n>`.
- `options` — seed events and/or creation metadata for the header.

**Returns** the live session, already entered and announced.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/core/session/src/index.ts#L606)

### ctx.sessions.prepare(id?, options?)

```ts website-api
/**
 * Build a session WITHOUT entering it into the store — validate the id/cwd and
 * construct the {@link Session} (with its immutable {@link SessionHeader}).
 * Pairs with {@link enter} + {@link announce}: a caller that owns a composite
 * `ctx.effect` (the agent factory) folds the session lifecycle into that ONE
 * effect so a fiber unload tears the session + agent down as a single ORDERED
 * chain rather than as racing sibling effects — which would remove the publication hooks
 * before the loop's closing `session/flush`, dropping the closing events.
 *
 * @param id - the session id; omitted, the store mints `session-<n>`.
 * @param options - seed events and/or creation metadata for the header.
 * @returns the constructed session, NOT yet in the store.
 * @throws if a session with `id` already exists, metadata is not a plain
 *   lossless-JSON record with valid scalar fields, or `meta.cwd` is a
 *   non-absolute path.
 */
prepare(id?: SessionId, options?: CreateSessionOptions): Session
```

Build a session WITHOUT entering it into the store — validate the id/cwd and construct the Session (with its immutable SessionHeader). Pairs with enter + announce: a caller that owns a composite `ctx.effect` (the agent factory) folds the session lifecycle into that ONE effect so a fiber unload tears the session + agent down as a single ORDERED chain rather than as racing sibling effects — which would remove the publication hooks before the loop's closing `session/flush`, dropping the closing events.

- `id` — the session id; omitted, the store mints `session-<n>`.
- `options` — seed events and/or creation metadata for the header.

**Returns** the constructed session, NOT yet in the store.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/core/session/src/index.ts#L635)

### ctx.sessions.enter(session)

```ts website-api
/**
 * Enter a {@link prepare}d session into the store: install the module-private
 * append publication hooks and add it to the store. Returns the DETACH
 * disposer (hooks + store removal). Does NOT emit `session/created` —
 * the caller yields this disposer inside its effect and THEN calls
 * {@link announce}, so a throwing `session/created` listener rolls the attach
 * back instead of leaking it.
 *
 * Re-checks the id for a duplicate: `prepare` and `enter` are public
 * cross-package primitives and a caller may interleave arbitrary work (or
 * another create) between them, so a stale prepared session must NOT overwrite
 * a live store entry of the same id — its detach disposer would later delete
 * the REAL session. The {@link create} convenience and the agent factory call
 * the two back-to-back so they never trip this, but the public seam cannot
 * assume that.
 *
 * @param session - a {@link prepare}d session not yet in the store.
 * @returns the detach disposer (publication hooks + store removal). When called from
 *   a synchronous `session/created` listener, removal and disposal wait until
 *   that creation dispatch unwinds.
 * @throws if a session with this id is already in the store.
 */
enter(session: Session): () => void
```

Enter a prepared session into the store: install the module-private append publication hooks and add it to the store. Returns the DETACH disposer (hooks + store removal). Does NOT emit `session/created` — the caller yields this disposer inside its effect and THEN calls announce, so a throwing `session/created` listener rolls the attach back instead of leaking it.
Re-checks the id for a duplicate: `prepare` and `enter` are public cross-package primitives and a caller may interleave arbitrary work (or another create) between them, so a stale prepared session must NOT overwrite a live store entry of the same id — its detach disposer would later delete the REAL session. The create convenience and the agent factory call the two back-to-back so they never trip this, but the public seam cannot assume that.

- `session` — a `prepare`d session not yet in the store.

**Returns** the detach disposer (publication hooks + store removal). When called from a synchronous `session/created` listener, removal and disposal wait until that creation dispatch unwinds.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/core/session/src/index.ts#L679)

### ctx.sessions.announce(session)

```ts website-api
/** Emit `session/created` exactly once for an {@link enter}ed session (with
 * the carrier {@link enter} captured). Separate from {@link enter} so the
 * caller can yield the detach disposer first (rollback safety — see
 * {@link enter}).
 * @param session - the entered session to announce to listeners.
 * @throws if the session is not live or its announcement already began,
 *   including a reentrant call from a creation listener. */
announce(session: Session): void
```

Emit `session/created` exactly once for an entered session (with the carrier enter captured). Separate from enter so the caller can yield the detach disposer first (rollback safety — see enter).

- `session` — the entered session to announce to listeners.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/core/session/src/index.ts#L734)

### ctx.sessions.flush(session)

```ts website-api
/**
 * Dispatch the awaited `session/flush` durability checkpoint for `session`,
 * with the carrier captured at {@link enter}. THE flush entry point: the
 * store owns the carrier, so callers (the loop's turn-end checkpoint, idle
 * injection, teardown drains) must come through here rather than dispatch a
 * raw `ctx.parallel('session/flush', …)` — one owner, one spelling, and the
 * scoped-dispatch invariant can pin it.
 * @param session - the session whose buffered events must reach durable storage.
 * @returns resolves when every flush listener has settled; after all settle,
 *   rejects with the first registered listener failure if any listener failed.
 */
async flush(session: Session): Promise<void>
```

Dispatch the awaited `session/flush` durability checkpoint for `session`, with the carrier captured at enter. THE flush entry point: the store owns the carrier, so callers (the loop's turn-end checkpoint, idle injection, teardown drains) must come through here rather than dispatch a raw `ctx.parallel('session/flush', …)` — one owner, one spelling, and the scoped-dispatch invariant can pin it.

- `session` — the session whose buffered events must reach durable storage.

**Returns** resolves when every flush listener has settled; after all settle, rejects with the first registered listener failure if any listener failed.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/core/session/src/index.ts#L786)

### ctx.sessions.get(id)

```ts website-api
/**
 * Look up a live session.
 * @param id - the session id to look up.
 * @returns the session, or undefined when no live session has that id.
 */
get(id: SessionId): Session | undefined
```

Look up a live session.

- `id` — the session id to look up.

**Returns** the session, or undefined when no live session has that id.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/core/session/src/index.ts#L818)

### ctx.sessions.list()

```ts website-api
/**
 * All live sessions, in creation order.
 * @returns a fresh array; mutating it does not affect the store.
 */
list(): Session[]
```

All live sessions, in creation order.

**Returns** a fresh array; mutating it does not affect the store.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/core/session/src/index.ts#L826)

### ctx.sessions.fork(source, boundary?, childSessionId?)

```ts website-api
/**
 * Create a live child session from a turn-enclosed prefix of a live source.
 * `boundary` is an inclusive source event seq; omitted means the source's
 * current last event. A non-empty selected slice must end at `turn/end`.
 *
 * @param source - Live source session object or id.
 * @param boundary - Inclusive source event seq to fork through; omitted means
 *   the source's current last event, and omitted on an empty source forks an
 *   empty child.
 * @param childSessionId - Optional child session id; omitted delegates to
 *   `SessionStore`'s id policy.
 * @returns The created live child session.
 */
fork(source: SessionForkSource, boundary?: number, childSessionId?: SessionId): Session
```

Create a live child session from a turn-enclosed prefix of a live source. `boundary` is an inclusive source event seq; omitted means the source's current last event. A non-empty selected slice must end at `turn/end`.

- `source` — Live source session object or id.
- `boundary` — Inclusive source event seq to fork through; omitted means the source's current last event, and omitted on an empty source forks an empty child.
- `childSessionId` — Optional child session id; omitted delegates to `SessionStore`'s id policy.

**Returns** The created live child session.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/core/session/src/index.ts#L843)
