1.7 KiB
Session Fork
The session fork service is an optional capability over the core session store. It does not add new log events or persisted record shapes; it packages the existing seed primitive into a safe service with a turn-boundary policy.
Package: @deepseek-ai/dsh-session-fork (ctx.sessionFork). The decision and rationale are recorded in the session fork service RFC.
Service Shape
SessionForkService.snapshot(source) accepts a live Session object or live SessionId, validates the source log is empty or ends at turn/end, then returns the resolved source, a deep-cloned SessionEvent[] seed, and child metadata: parentSession, seedLength, and optional inherited cwd.
SessionForkService.fork({ source, sessionId? }) is a convenience wrapper around ctx.sessions.create(sessionId, { seed, meta }). Consumers that create agents can use snapshot() directly and pass the returned seed/meta through the agent factory instead of creating a detached session first.
Boundary Policy
The boundary rule is structural: every turn/end reason is forkable, and every non-empty log whose last event is not turn/end is rejected. This is intentionally stricter than the subagent fork backend, which clips to the parent's last completed-turn prefix because it is usually invoked from inside the parent's active tool turn.
Persistence
No persistence method is added. A forked child is just a normal live session with seed events already present at creation time, so existing persistence backends persist the inherited prefix and header metadata through session/created and session/flush.