Files
deepseek-harness/packages/subagent
Tianyi Cui 1a81f2cccd Add subagent capability seam: interface, mock backend, model-facing tool
Introduce the `packages/subagent/` group and the abstract subagent seam — an
agent delegating to a child agent — as a named-provider registry (`ctx.subagents`),
unlike the single-implementation bash seam, so multiple transports (in-process,
ACP, future A2A) coexist. This first PR lands the interface, a scripted test
backend, and the model-facing tool, validated through the real cordis load path.

- dsh-subagent: SubagentService registry + SubagentProvider/SubagentRun
  vocabulary + subagent/start|end events. Start-time capabilities (outputSchema,
  depthLimit, toolFilter) are checked pre-start and rejected loud; runtime
  capabilities (sendMessage, resume) are optional methods on SubagentRun.
- dsh-subagent-mock (support): scripted provider for keyless, deterministic
  tests through the real Loader/export path.
- dsh-tool-subagent: the model-facing `subagent` tool, config-bound to one
  provider; synchronous collect with try/finally dispose, signal->cancel
  bridging, and non-completed-stop-reason -> isError mapping.
- Proposed RFC documenting the seam, the fork-vs-spawn-as-separate-backends
  decision, own-session isolation, synchronous-collect scope, and the deferral
  of background/poll/spill to a future unification with bash.
- Wire the new group into tsconfigs, build refs, package hierarchy docs, the
  module graph, and the cordis catalog.

RFC: docs/rfc/proposed/feature/2026-06-21-subagent-capability-seam.md
2026-06-21 22:31:56 +08:00
..

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
tool-subagent/ Model-facing subagent delegation tool over ctx.subagents (registers on ctx.tools)

The interface lives at subagent/subagent/. Provider implementations live in their own packages — the in-process dsh-subagent-spawn / dsh-subagent-fork and the out-of-process dsh-subagent-acp — plus the test-only dsh-subagent-mock in support. All product packages except the mock.

The proposal and design rationale: docs/rfc/proposed/feature/2026-06-21-subagent-capability-seam.md.