deepseek-harness/packages/subagent

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.