Code Mode was a deployment-wide field on the host `tools` row: a deployment ran every session that way or none. The obvious product shape — 代码模式 beside 标准/极简/创造 in the preset picker — had nothing to hang on. The registry itself cannot move into a preset; the agent loop's scheduler, the api-proxy's presenters, and every tool plugin are its consumers. So split the registry from its projection: `presentAs(mode)` writes one cell on the calling agent's scope layer, exactly as `restrict()` does, and the three reads that decided presentation take that scope's mode instead of the service's. The config `mode` becomes the default agents shadow rather than a process-wide fact. Two consequences are load-bearing. `run_code` now enters a view only for scopes whose own mode presents it — a native agent must not find it dispatchable because another agent in the process does — and the reserved name holds whatever the configured mode, since any agent may select a code mode later. `dsh-agent-tool-mode` is the row a preset carries to declare this. A code mode waits for the host's `codeRuntime` rather than assuming it, so a runtime-less deployment fails the preset at mount, naming the row, instead of at the session's first request. The shipped `code` preset is `standard` plus that row, ordered second.
core/ — product API spine
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The session log, system-prompt assembly, tool registry, agent vocabulary, and concrete loop that form the harness's default control spine. These are product packages — the stable surface plugins and consumers build against.
| Package | Role | ctx key |
|---|---|---|
scope/ |
Scoped-context registration primitive | library — no ctx key |
session/ |
Event-sourced session log and in-memory store | ctx.sessions |
system-prompt/ |
Prompt and tool-schema assembly registry | ctx.systemPrompt |
tools/ |
Scoped tool registry and execution pipeline | ctx.tools |
agent/ |
Agent interface, registry, and event vocabulary | ctx.agents |
agent-loop/ |
Default concrete agent driver | ctx.agentLoop |
scope supplies the shared scoping primitive. agent owns the public seam, while agent-loop is its default implementation; extension plugins depend on the seam so the driver remains swappable.
Runnable compositions belong to examples/agent-spine-demo; this group owns only the swappable spine pieces.