A Codex review pass on the draft caught four real gaps and two solid suggestions; all addressed except one pushed back on the merits: - hooks-claude/hooks-codex: stderrSummaryMaxChars was the one new knob with NO range validation — a negative/NaN cap would silently misbehave inside slice(). Both bridges now assert a positive integer at the TOP of apply() (before the config-file parse's early return, so a bad value fails the load loudly), with rejection tests. - tool-fs: the read caps count lines/chars/bytes, so positive-FINITE was too loose (a fractional readLimit would flow into windowing arithmetic and the schema description). All four now require a positive integer, matching tool-web's cap. - Doc drift the gates cannot catch: tool-web's README tools table still named WEB_SEARCH_MAX_RESULTS as the mechanism; compact-basic's README/module doc and the compaction-capability-seam RFC still described estimation as fixed char/4 rather than the charsPerToken default. - subagent-acp: the dispose graces were tested only at the startAcpRun level, so a regression that stopped threading plugin config into AcpRunSpec would have survived. A provider-path test now drives the trap-escalation scenario through ctx.subagents.start with small config graces and bounds dispose at 4s. Pushed back on: converting compact-basic's charsPerToken to a schemastery field. The package's whole config is deliberately hand-rolled (resolveConfig, every threshold REQUIRED with no default — a documented design posture); one schemastery field beside it would be incoherent. The knob is cordis.yml-reachable, defaulted, and validated, which is what the convention requires; migrating the package to schemastery wholesale is pre-existing config-surface hygiene out of this change's scope.
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.