6d389d261e
The implementation no longer stores inherited policy in SessionHeader or resolves a second baseline chain, but the feature, sandbox, and approval notes still described that machinery. Keeping those claims would make the smaller design look incomplete and invite reintroduction of the generic persistence surface. Rewrite the owning feature note around the actual delegation snapshot: source-tagged policy events follow the optional fork prefix, ordinary last-event-wins folds establish precedence, and persistence captures the constructor seed with the first materialized batch. Condense the alternatives and consequences to the decisions and coverage that remain load-bearing. Align the sandbox and approval notes plus the subagent-inprocess consumer README with that contract. Update the four Chinese counterparts minimally and re-record each pairing hash so both languages describe the same shipped mechanism.
subagent/ — subagent capability family
English | 中文
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 (no provider; one cleanup effect per run) | — |
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) |
subagent-dsh-sdk/ |
Out-of-process backend: a child harness runtime in a spawned subprocess, driven over stdio JSON-RPC through the TypeScript SDK client | (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 library with no provider of its own — both depend on it, neither on the other), and the out-of-process subagent-acp / subagent-dsh-sdk backends spawn their children through the subprocess/ seam (the shared credential scrub, tree-scoped teardown, and dispose ladder). Tests replace only the child boundary with package-local fixtures.
The proposal and design rationale: .agents/notes/implemented/feature/2026-06-21-subagent-capability-seam.md.