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A cancel that lands AFTER a child's clean turn end but before the nudge continuation runs clears nothing — child.cancel() only kills queued or running work — so the loop's turn-state check alone let a later child.send() spend a fresh post-cancellation turn (and even capture a structured result the caller had already abandoned). The loop condition now also reads the run's own cancelled flag, re-evaluated after every whenIdle(), through an accessor because closure assignments are invisible to control-flow narrowing (an inline read lints always-true). readResult keeps the outcome honest on this path: a completed-but- uncaptured turn maps to aborted, not error, when a cancel is why the nudging stopped — the cancel contract outranks the schema shortfall.
subagent/ — subagent capability family
The subagent seam: an agent delegating work to a child agent. Like the bash and llm families this is a capability seam (see capability seams) — but with one defining difference: multiple provider implementations coexist in one context, registered by name, rather than the single-implementation bash shape. The registry mirrors the LLM adapter registry.
| Package | Role | ctx key |
|---|---|---|
subagent/ |
Abstract subagent seam: named-provider registry + vocabulary | ctx.subagents |
subagent-inprocess/ |
Shared in-process run driver (pure lib; registers nothing) | — |
subagent-spawn/ |
In-process backend: a fresh child agent | (registers on ctx.subagents) |
subagent-fork/ |
In-process backend: a child seeded with the parent's completed-turn prefix | (registers on ctx.subagents) |
subagent-acp/ |
Out-of-process backend: a child agent in a spawned subprocess, driven over ACP | (registers on ctx.subagents) |
tool-subagent/ |
Model-facing subagent delegation tool over ctx.subagents |
(registers on ctx.tools) |
The interface lives at subagent/subagent/. The in-process subagent-spawn / subagent-fork backends share the subagent-inprocess driver (a pure library — both depend on it, neither on the other), and the out-of-process subagent-acp backend ships alongside them here; the test-only dsh-subagent-mock (in support) is separate. All product packages except the mock.
The proposal and design rationale: docs/rfc/implemented/feature/2026-06-21-subagent-capability-seam.md.