description: "The core group map: the session log, system-prompt assembly, tool registry, agent vocabulary, and default loop that form the product API spine."
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Use the core packages to build or extend an agent that records durable session history, assembles system prompts, exposes tools, selects a default model, and runs model turns. These packages define the shared APIs used by every composition, while executable product assemblies live under packages/bundle. Choose this group when developing agent behavior or replacing one of those capabilities; start with dsh-base when you need the default runnable composition.
| Package | Role | ctx key |
|---|---|---|
scope/ |
Scoped registration and event routing that isolate one agent's contributions | library — no ctx key |
session/ |
The append-only session event log every agent's history derives from | ctx.sessions |
system-prompt/ |
System-prompt assembly from ordered sections, tool schemas, and variables | ctx.systemPrompt |
tools/ |
The tool registry and guarded execution pipeline the loop dispatches through | ctx.tools |
agent-tool-presentation/ |
Per-agent tool-presentation selector for presets | no ctx key |
agent/ |
The Agent handle plugins program against, plus its live registry and events |
ctx.agents |
agent-default-model/ |
The deployment default model selection entry points apply to fresh agents | ctx.agentDefaultModel |
agent-loop/ |
The default agent driver: creates agents and runs the turn and step lifecycle | ctx.agentLoop |
scope supplies the shared scoping primitive; agent owns the public Agent contract, while agent-loop is its default implementation, so extension plugins depend on agent and the driver stays swappable. agent-default-model owns the deployment selection an entry point applies when a session has none of its own. Runnable compositions live under packages/bundle; this group owns only the swappable spine pieces.
Agent handle contracts.