Tianyi Cui
b3d40d427e
A fork subagent seeds its child session with a prefix of the parent's log, and that seed becomes the child's persisted log — so a fork child's .jsonl begins with the PARENT's events, including the parent's assistant/chunk events. The snapshot replay harness derived a child's script from its whole log, which would replay the parent's recorded responses as the child's model calls. Spawn-only scenarios never hit it, but a fork snapshot would mis-route silently. Record the seed boundary and skip the inherited prefix at replay: - SessionHeader gains an optional `seedLength` (how many leading events were inherited via a seed), threaded through CreateSessionOptions/CreateAgentOptions meta and stamped by the fork backend (= seeded-prefix length; absent for spawn). It is EXPLICIT, never inferred from seed.length: a resume seeds the whole stored log, so the resume path passes the persisted boundary back. - Both persistence backends round-trip it: JSONL header line, SQLite seed_length column. The SQLite table change bumps SCHEMA_VERSION 2->3; per the pre-release stance the backend rejects an older user_version on open with NO migration. - llm-replay's parseSessionHeader reads seedLength and loadSessionScripts derives a child script from events AFTER the boundary. seedLength is 0 for spawn, so spawn replay is byte-for-byte unchanged. Closes the routing-correctness gap the per-session snapshot replay RFC under- stated; a recorded fork scenario remains a future addition but now derives correctly. RFC: docs/rfc/implemented/testing/2026-06-22-fork-child-replay-seed-boundary.md. Regression coverage: a fork child fixture whose seeded prefix carries a parent chunk (derived script must exclude it, proven red without the slice); a seedLength persistence round-trip through the shared coordinator contract (both backends); the fork backend stamping it; resume preserving it from the persisted header.
@deepseek-ai/dsh-subagent-inprocess
The shared in-process subagent run driver. A pure library (no provider, no registration) that the in-process backends — spawn (a fresh child) and fork (a child seeded with a prefix of the parent's log) — both build on. The backends are thin shells that differ ONLY in the session seed they pass; everything downstream lives here, so neither backend depends on the other.
What it exports
startInProcessRun(ctx, request, options): SubagentRun
Runs a child as a child Agent on the same cordis context (ctx.agents):
- computes child depth =
depthOf(parent) + 1; ifrequest.maxDepthis set and exceeded, throwsSubagentDepthError(thedepthLimitcapability); - creates a child via
ctx.agents.createwith a freshAgentId/SessionId, the parent'scwd+parentSessionlineage, the optionaloptions.seed(fork's completed-turn prefix; omitted for a fresh child), andagentOptions(the child inherits the parent's model by default — a child with no model can't run — overridable viarequest.agentOptions.model; the system prompt is NOT inherited); - drives the one-shot:
child.send(prompt)thenawait child.whenIdle()(ordering matters —sendenqueues synchronously, sowhenIdleobserves the queued work and resolves on the child'srunning → idletransition, never before the turn starts); - reads the result, scoped to the child's OWN events (everything at or after
seedLength, so a seeded child that produced no message of its own never returns the seeded parent's last message): the lastassistant/messagecontent (deep-cloned — the log is frozen) and the lastturn/end.reasonmapped to aSubagentStopReason.
dispose() delegates to AgentHandle.dispose() (stop loop → await quiescence → remove session); cancel() cancels the child's in-flight turn. A cancel landing before any turn/end (the pre-turn window) still settles aborted, honoring the cancel contract rather than the generic no-turn error.
InProcessRunOptions
{ providerName: string; seed?: SessionEvent[] } — the per-backend inputs: the provider name (for error context) and the optional child-session seed.
depthOf(agent): number
Delegation depth rides on a merge-extensible AgentOptions.subagentDepth field (0 for a top-level agent, parent + 1 for a child), so a nested spawn reads its parent's depth from parent.options.subagentDepth. depthOf reads it (absent ⇒ 0).
SubagentDepthError
Thrown by startInProcessRun when a spawn would exceed the request's maxDepth cap; carries attemptedDepth and maxDepth.