a3244a5774
The partial-toolFilter materialization fix (da6c6d58) stopped one field
short: the adjacent agentOptions key in the SAME Config has the same
schemastery trap. An omitted agentOptions materializes {}, which is truthy —
so every yml-configured load put a dishonest agentOptions: {} on every start
request and the presence check in execute() could never be false through
config (only unit tests bypassing schemastery ever exercised that branch).
Harmless downstream today (the driver only spreads it), but the request
shape lied and the check was production-dead.
Same discipline as its toolFilter sibling: the omitted key now defaults to
undefined, the presence check is spelled !== undefined like its neighbors,
and a regression test (fails against the unfixed schema) pins that an
omitted agentOptions stays absent from the request. Swept every other
Config in the repo for the class: no further instances — omitted primitives
inside a materialized object stay ABSENT (verified empirically), so
subagent-mock's capabilities spread is safe, and the remaining object/array
fields all carry explicit defaults or the forced-undefined discipline
already.
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.