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.
AgentLoop (ctx key: agentLoop)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.agents, sessions, llm, tools, systemPrompt — all five interface
services.
Config: {
agents: Array<{
id: string // required
model?: string
systemPrompt?: string
}>
}
Agents listed in config are auto-created at startup.
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.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.
Everything that goes beyond "call the model, run the tools, repeat" belongs to plugins listening on the event taxonomy:
agent/request, agent/step-result, tools/execute, agent/turn-continuationagent/requesttools/executeAgentLoop.create()session/event + session/flushagent/stream-chunk + agent/* events