Tianyi Cui
7aabd2a3df
The second PR of the subagent seam: the two in-process backends that run a
child agent on the same cordis context, reusing the agent factory's quiescent
AgentHandle teardown. Both register on ctx.subagents (PR1's named-provider
registry) and share one run driver.
- dsh-subagent-spawn: a FRESH child via ctx.agents.create — own session, the
parent's model by default (overridable), zero inherited conversation. Also
exports the shared in-process run driver (startInProcessRun): mint ids, stamp
cwd/parentSession-lineage/depth, drive the one-shot (send → whenIdle), read
the last assistant/message + turn/end reason, dispose to quiescence.
- dsh-subagent-fork: a child SEEDED with the parent's balanced completed-turn
prefix (the log up to and including its last turn/end), so the child inherits
context. The in-flight unbalanced turn is excluded — a raw seed would fail the
invariants replay. Proven: a regression test goes red if the boundary seeds
the open turn.
- Seam extension: CreateAgentOptions.seed, threaded through AgentLoop.createAgent
→ ctx.sessions.prepare({ seed }) (the primitive resume already used). This is
the fork-lineage path the TODO(sub-agents) markers anticipated.
- Depth: a merge-extensible AgentOptions.subagentDepth (0 top-level, parent+1 for
a child); the depthLimit capability refuses a spawn past request.maxDepth.
Tests: real-loop unit tests for both backends (mock MODEL only, real loop +
invariants), a multi-subagent test (one parent drives a fork AND a spawn child
then keeps working), and a with-key e2e (a real parent delegates via the
`subagent` tool to a real child that writes a file on disk — world-verified).
100% per-file coverage. The coding-agent demo wires the spawn backend + tool.
Snapshot coverage of nested agents is deferred to a stacked follow-up
(TODO(subagent-snapshots)): dsh-llm-replay is a single global positional cursor
that cannot route calls to a parent vs. a child on one context. Recorded in the
RFC's deferrals and a new AGENTS.md rule: designing a subsystem must design its
test infrastructure END TO END up front, verifying the snapshot/e2e harness can
express the new shape — a gap this plan hit.
Examples
Runnable demos (not workspaces) that showcase how the harness is wired. Each example is now a thin leaf: a cordis.yml that picks the swappable backends (an LLM adapter, a bash executor) and loads ONE app package, plus any demo-only mocks. The composition — the spine, the front-door cluster, and the boot glue — lives in the app packages (@deepseek-ai/dsh-stdio-agent, @deepseek-ai/dsh-acp-agent) and the @deepseek-ai/dsh-agent-core bundle they share. There is no start.ts; the demo:* scripts invoke each app package's bin.
echo-agent
A mock model + echo tool on the stdio chat app — the all-mock skeleton. The leaf swaps dsh-stdio-agent's LLM backend to a local mock-echo adapter and adds a local echo tool. Demonstrates:
- A thin leaf
cordis.ymlloading the@deepseek-ai/dsh-stdio-agentapp - Registering a mock
LlmAdapter(streaming scripted responses) - Registering a tool via
ctx.tools.register() - "Swap the backend, keep the app" — the only difference from
coding-agentis the adapter
Run with: pnpm run demo:echo. When prompted, type "echo " to trigger a tool call round-trip.
coding-agent
The real thing: DeepSeek V4 + the bash tool suite on the same @deepseek-ai/dsh-stdio-agent app. Where echo-agent proves the skeleton with mocks, this is a usable coding assistant.
Run with: pnpm run demo:coding (needs DEEPSEEK_API_KEY in the environment or a gitignored repo-root .env). See coding-agent/README.md for details.
acp-agent
The same coding agent exposed as an Agent Client Protocol (ACP) server over JSON-RPC stdio, via the @deepseek-ai/dsh-acp-agent app — drive it from Zed or any other ACP client. Also the home of the keyless snapshot tests.
Run with: pnpm run demo:acp (needs DEEPSEEK_API_KEY). See acp-agent/README.md for the Zed setup and the snapshot-test design.