05b75abbca
Pin the three-domain rule (session = durable fact log, agent = live runtime surface, tools = registry/exec): a durable replayable fact is a SessionEvent; a live interception or transient/live-object signal is an agent/tools Cordis event. A boundary that is both is mirrored as an agent/* emit ONLY where a live consumer needs the Agent handle. Apply it to the boundary twins: drop agent/step-start and agent/step-end (no production consumer needs the live Agent at a step boundary — consumers read the durable step/start/step/end session events). Keep agent/turn-start/turn-end (the stdio UI labels output by agent.id). Tests that observed step boundaries via the removed emits now observe the durable session events; the pinned behavior is unchanged. Conservative subset of the proposed "remove boundary mirror events" simplification; foundation for the Hooks subsystem's canonical event surface.
core/ — product API spine
The packages every harness build is assembled from: the session log, the system-prompt assembly, the tool registry, the agent vocabulary, and the one concrete loop that drives them. These are product packages — the stable surface plugins and consumers build against.
| Package | Role | ctx key |
|---|---|---|
session/ |
Event-sourced session log + in-memory store | ctx.sessions |
system-prompt/ |
Prompt-section + tool-schema assembly registry | ctx.systemPrompt |
tools/ |
Tool registry + tools/execute waterfall |
ctx.tools |
agent/ |
Agent interface, registry, agent/* event vocabulary |
ctx.agents |
agent-loop/ |
The concrete loop plugin: ReactLoopAgent + the loop driver |
ctx.agentLoop |
agent-core/ |
Bundle plugin: the providerless/executor-less/UI-less spine as code | (loads the spine) |
agent-loop is the one concrete implementation of the agent seam and lives here because it is the harness's default product loop; everything else in core/ is interface/vocabulary. Plugins depend on the agent vocabulary, never on agent-loop directly, so the loop stays swappable.
agent-core is the composition counterpart: one bundle plugin that loads the whole providerless spine (timer + llm + sessions + system-prompt + tools + agents + invariants + tool-bash + agent-loop) and forwards agent-loop's agents list as its own config. App packages (ui/stdio-agent, ui/acp-agent) consume it and add only a front door; a leaf adds only the swappable backends. It lives in core/ because it composes exclusively core/ + interface packages and ships no provider, executor, or UI of its own.