@destiner/pi-subagents

Subagents for pi, with one dial: intelligence.

The agent picks low, medium, or high. Your settings decide which model and thinking level that means, per parent model. The agent never picks a model name, and you never re-teach it your model preferences.

Install

pi install npm:@destiner/pi-subagents

The extension registers a single tool, agent. It won't load alongside another extension that registers a tool of the same name — remove the other one first.

Configure

Add one key to ~/.pi/agent/settings.json, keyed by the model driving the parent session. Nothing works until you do: an unmapped parent model is an error, not a fallback.

{
  "defaultModel": "claude-opus-5",

  "@destiner/pi-subagents": {
    "pi-claude/claude-opus-5": {
      "low": { "model": "pi-claude/claude-haiku-4-5", "effort": "medium" },
      "medium": { "model": "pi-claude/claude-sonnet-5", "effort": "medium" },
      "high": { "model": "pi-claude/claude-opus-5", "effort": "medium" },
    },
    "openai-codex/gpt-5.6-sol": {
      "low": { "model": "openai-codex/gpt-5.6-sol", "effort": "low" },
    },
  },
}

• Keys and model values are exact provider/model-id. No fuzzy matching, no bare ids, no date-stamp tolerance — a typo is an error, not a surprise model. Only the first slash separates the provider, so openrouter/deepseek/deepseek-v4-flash-0731 works.
• effort is a pi thinking level (off, minimal, low, medium, high, xhigh, max) and is optional; omitted, it uses your defaultThinkingLevel. pi clamps it to what the model supports.
• Levels are independent. Define only low if that's all you want — asking for anything else then fails and tells the agent what it can have instead.
• A project's .pi/settings.json overrides the global config per parent model.
• Config is read on every call, so edits apply without restarting pi.

Use

agent({
  description: "audit auth flow",
  intelligence: "medium",
  prompt: "…everything the subagent needs to know…"
})

The subagent starts from an empty context: it sees the prompt and nothing else, returns one text response, and cannot ask questions. Several calls in one turn run concurrently.

Errors

All three arrive as tool errors, so the agent sees them and can adjust:

Situation	Message
Parent model not in the config	Not available for this model (pi-claude/claude-opus-5)
Level not configured for it	This agent intelligence level is not available for this model. Available options: [low, high]
Configured model has no auth	Configured subagent model "…" for intelligence "low" is not available.

For RPC clients

details is the interface, streamed as tool_execution_update.partialResult and repeated on the final result:

{
  description: string;
  intelligence: "low" | "medium" | "high";
  model: string;            // resolved "provider/model-id"
  effort: ThinkingLevel;    // after pi's clamping
  status: "running" | "done" | "error";
  elapsedMs: number;
  toolCalls: number;
  currentTool?: string;
  text: string;             // the subagent's text so far
  usage: { input, output, cacheRead, cacheWrite };
}

Updates fire when the subagent starts, on each of its tool calls, and at the end of each of its messages — so text arrives in message-sized chunks rather than token by token.

What it deliberately doesn't do

No agent types or roles, no agent files, no background runs, no steering, no turn limits, no worktree isolation, no context inheritance. Subagents get the same tools as the parent minus agent itself, which is also the whole of the recursion guard. If the parent aborts, its subagents abort.

Two consequences worth knowing. The subagent inherits every extension and MCP tool configured in your settings, so a large MCP surface makes even a low call expensive in input tokens. And it loads extensions from settings only — extensions passed on the command line with -e don't reach it.