The spawn provider creates a fresh child Agent in the current process. The child has its own session, sees no parent conversation history, and reuses the host's agent factory and LLM/tool services.

Behavior

start(request) delegates to startInProcessRun with no seed and awaits publication before returning. The child receives parent working-directory/session lineage and inherits the parent model unless overridden, but starts with an empty conversation.

The shared driver owns depth checking, persona and tool-filter setup, structured output, required-signal cancellation, one-shot execution, result reading, and quiescent disposal. A startup rejection leaves no published child; provider unload after fulfillment does not revoke the holder-owned run.

Capabilities

Spawn advertises { outputSchema: true, depthLimit: true, toolFilter: true, persona: true } because it controls the child's creation window and can enforce all four features.

Config

Key	Meaning
`providerName`	Registry name on `ctx.subagents` (default `spawn`).

Model Experience

Context surface	What the model sees	Token effect
Child-agent request	The fresh child receives the standalone task, inherits the parent model and workspace by default, and sees the globally composed prompt and tools after its scoped persona and tool filter. It receives zero parent conversation messages.	The child pays for a new independent context and history; no parent-history tokens are duplicated.
Parent tool result, indirectly	Through `dsh-tool-subagent`, the parent receives only the child's final output or stop-reason error.	Parent input grows by one data-dependent result retained until compaction.

Known Limitations and Deferred Work

Runs expose no sendMessage/resume — the optional runtime capabilities are absent on in-process runs.
Fresh means no parent transcript — the child inherits cwd, lineage, model, and explicitly configured persona/tool restrictions, but none of the parent's conversation; use the fork provider when completed-turn context is required.