Tianyi Cui
df4b7d3d9a
Add the durable session-persistence capability seam (ADR 0016): an
abstract SessionPersistence service (dsh-session-persistence,
ctx.sessionPersistence) defining create/append/load/list/has/delete/
update over the existing SessionEvent — no parallel persisted type — and
a first implementation (dsh-session-persistence-jsonl): an append-only
JSONL log per session with crash-safe atomic writes, truncation-repair
of a never-committed crash tail, and a read/replay path. SessionMeta
(format version, cwd, lineage) travels out-of-log via session.header.
A shared runPersistenceContract suite holds every backend to the same
append-only / contiguous-seq / lazy-materialization / serializability
semantics.
Config-driven create() now uses a per-run ${id}-session-<uuid> session
id so a fixed name no longer collides with an on-disk log once a durable
backend is loaded; each run is a new session (a demo simplification). The
examples drop their hand-rolled session-jsonl.ts and load the JSONL
backend via cordis.yml; CI smoke-loads it too.
The agent-facing create/resume factory that consumes load() is a
separate seam, deferred to a follow-up; this change stops at the load
primitive and does not reach into the loop.
73 lines
2.9 KiB
Markdown
73 lines
2.9 KiB
Markdown
# dsh-agent-loop
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THE concrete agent plugin: `LoopAgent` and the loop driver. Implements the `Agent` interface and drives the session/turn/step lifecycle.
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This is the only package in the harness that contains concrete loop logic. Everything else is an abstract service or a plugin against extension seams — new behavior goes into plugins, not here.
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## Service: `AgentLoop` (ctx key: `agentLoop`)
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### Public API
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- `ctx.agentLoop.create(id: string, options?: AgentOptions): LoopAgent` — create an agent on a fresh per-run session id `${id}-session-<uuid>`, start its loop, and register it in `ctx.agents`. The per-run uuid avoids colliding with the on-disk log a prior run materialized once a durable persistence backend is loaded; each run is a new session (a deliberate demo simplification — a real resume-or-create policy is a TODO). Disposed with the calling fiber.
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### Injected services
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`agents`, `sessions`, `llm`, `tools`, `systemPrompt` — all five interface services.
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### Configuration (schemastery)
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```ts
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interface Config {
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agents: Array<{
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id: string // required
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model?: string
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systemPrompt?: string
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}>
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}
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```
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Agents listed in config are auto-created at startup.
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### Classes
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- `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.
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- `Inbox` — per-agent queued + steering FIFOs (`enqueue`, `steer`, `drainQueued`, `drainSteering`, `waitForQueued`).
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### Loop lifecycle (`loop.ts`)
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One invocation of `runLoop()` drives one agent for its whole lifetime:
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```
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forever:
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wait for queued messages (idle)
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TURN (error-contained):
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drain queued → 'turn/start' → session('user/message')
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STEP loop:
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drain steering
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assembly = systemPrompt.assemble()
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request = waterfall agent/request
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stream llm.stream(request) → session('assistant/chunk')
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message = waterfall agent/step-result
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session('assistant/message')
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each tool-call: session('tool/call') → tools.execute() → session('tool/result')
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drain steering → session('steering/message')
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cont = waterfall agent/turn-continuation
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if !cont: break
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session('turn/end')
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await session/flush
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re-enqueue leftover steering as queued
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idle unless more queued
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```
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Error containment: a throwing plugin ends the **turn**, never the loop. Dispose mid-turn emits `agent/status('disposed')` and ends with reason `disposed`.
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### What is NOT here
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Everything that goes beyond "call the model, run the tools, repeat" belongs to plugins listening on the event taxonomy:
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- Hooks: `agent/request`, `agent/step-result`, `tools/execute`, `agent/turn-continuation`
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- Compaction: `agent/request`
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- Sandbox, permission, plan mode: `tools/execute`
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- Sub-agents: TODO seam on `AgentLoop.create()`
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- Persistence: `session/event` + `session/flush`
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- UI: `agent/stream-chunk` + `agent/*` events
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