8df89d8e33
Codex review of PR-A found three blockers: - A throwing step/start session-event listener left an unbalanced log (turn/start → step/start → turn/end with no step/end), which the invariants oracle rejects — masked because that rejection was itself contained as a throwing turn/end listener. Fix the root cause in the loop: mark the step open BEFORE appending step/start (Session.append pushes before notifying), so the outer catch's closeStep() appends the balancing step/end. The test now asserts the balanced outcome (stepEnd:1, step/end before turn/end); proven load-bearing (revert the reorder → the test goes red with stepEnd:0). - Reintroduce the /goal-pattern guard deleted in the prior commit, migrated to a step/end session-event listener (the surviving step-boundary hook point), with a no-tools first step so it exercises the hasSteering continuation override. - Update packages/core/agent/README.md: step boundaries are no longer agent/* emits.
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.