280233ba78
The cross-seam blocker: structured_output recorded its value in the tool BODY, before tools/post-execute could block the call — a PostToolUse hook's block turned the logged result into isError while readResult still returned structured success and the continuation veto ended the turn. Two-phase commit: the body validates and STAGES (RunState.pending); a fourth runtime listener on tools/post-execute — prepend, so await next() returns the composed final decision — promotes the stage to captured only on an accepted call, and clears it on every path. A block now yields a consistent pair: the model and log see the isError feedback, the run settles error with no structured value, and the turn continues so the model can react. Regressions: block denies the capture end-to-end; accept-with-replacement still commits.
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.