Files
deepseek-harness/packages/agent-loop
Tianyi Cui 0731ed374b feat(session): metadata seam + JSON-serializability invariant
Adds the durable-session metadata seam and enforces the log's
JSON-serializability invariant at the source:

- SessionHeader / SessionSummary / SessionMeta and CreateSessionOptions in
  dsh-session; Session gains a readonly `header`; SessionStore.create takes
  `(id?, options?: { seed?; meta? })` (validated absolute cwd, parentSession
  lineage). The injection TurnTrigger variant is added for the idle-inject
  one-shot turn that a later change introduces.
- isJsonValue (new json.ts): a value round-trips through JSON losslessly —
  rejects BigInt, function, symbol, undefined, non-finite numbers, sparse
  arrays, circular refs, and exotic objects (Map/Set/Date/class instances).
- Session.append throws on non-JSON-serializable data, and the Session
  constructor validates every seed event (isJsonValue + contiguous seq from
  0), so a replay/fork seed can never build a live log no backend can
  persist — the source-level guarantee a durable backend relies on.

Migrates the ~3 internal positional-seed `create(id, seed)` call sites to
`{ seed }`, and adapts the invariants tests forced by the new guard (the
bad-seq seed is now caught by the constructor; the cyclic deep-freeze test
drives via session/event since append rejects cyclic data; a direct
session/event drives the invariants seq-monotonicity check). Docs kept
backend-agnostic (the persistence packages arrive in a later PR).
2026-06-15 17:54:55 +08:00
..
2026-06-11 10:54:31 +08:00

dsh-agent-loop

THE concrete agent plugin: LoopAgent and the loop driver. Implements the Agent interface and drives the session/turn/step lifecycle.

This is the only package in the harness that contains concrete loop logic. Everything else is an abstract service or a plugin against extension seams — new behavior goes into plugins, not here.

Service: AgentLoop (ctx key: agentLoop)

Public API

  • ctx.agentLoop.create(id: string, options?: AgentOptions): LoopAgent Create an agent, start its loop, and register it in ctx.agents. Disposed with the calling fiber.

Injected services

agents, sessions, llm, tools, systemPrompt — all five interface services.

Configuration (schemastery)

interface Config {
  agents: Array<{
    id: string                 // required
    model?: string
    systemPrompt?: string
  }>
}

Agents listed in config are auto-created at startup.

Classes

  • LoopAgent — the concrete Agent implementation. Owns the inbox (Inbox), the per-step AbortController, and the loop driver. Everything observable happens through session events and the agent/* event taxonomy.
  • Inbox — per-agent queued + steering FIFOs (enqueue, steer, drainQueued, drainSteering, waitForQueued).

Loop lifecycle (loop.ts)

One invocation of runLoop() drives one agent for its whole lifetime:

forever:
  wait for queued messages (idle)
  TURN (error-contained):
    drain queued → session('user/message') → 'turn/start'
    STEP loop:
      drain steering
      assembly = systemPrompt.assemble()
      request = waterfall agent/request
      stream llm.stream(request) → session('assistant/chunk')
      message = waterfall agent/step-result
      session('assistant/message')
      each tool-call: session('tool/call') → tools.execute() → session('tool/result')
      drain steering → session('steering/message')
      cont = waterfall agent/turn-continuation
      if !cont: break
    session('turn/end')
    await session/flush
    re-enqueue leftover steering as queued
  idle unless more queued

Error containment: a throwing plugin ends the turn, never the loop. Dispose mid-turn emits agent/status('disposed') and ends with reason disposed.

What is NOT here

Everything that goes beyond "call the model, run the tools, repeat" belongs to plugins listening on the event taxonomy:

  • Hooks: agent/request, agent/step-result, tools/execute, agent/turn-continuation
  • Compaction: agent/request
  • Sandbox, permission, plan mode: tools/execute
  • Sub-agents: TODO seam on AgentLoop.create()
  • Persistence: session/event + session/flush
  • UI: agent/stream-chunk + agent/* events