Codex diff review, round 1, two (A) findings: - The agent/request fallback resolved the RAW seed object — on later steps the session's cached header fold — so a delegating listener (await next(), mutate, return) could rewrite the fold in place and the change would compare as already-baseline: no delta logged, the persisted log unable to reconstruct the request (the dev invariant would fire on the divergence, but the log would still lie). One structuredClone'd, deep-frozen seed now serves both the listener chain and the fallback — in-place shaping after delegation throws — and Session.requestHeader() freezes its fold on update, so the leak class is unrepresentable from either side. Pinned by a loop-level delegating-mutator test. - Doc sweep for the old contract: agent README's event row (mutate GenerateOptions / tool filtering → frozen config seed, replacement out, logged header), compact-basic's module JSDoc (summarize routed through agent/request → direct one-shot at llm/stream), and architecture.md's event-domain line (request mutation → call-config shaping).
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/pre-execute/tools/post-execute pipeline |
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 the swappable backends plus any optional product tools it wants to expose. It lives in core/ because it composes exclusively core/ + interface packages and ships no provider, executor, or UI of its own.