@d3ara1n/pi-scout

Per-turn side agent decision framework for pi.

Before each conversation turn, scout analyzes the user's prompt and makes routing decisions:

1. skill-router — Selects which skills to advertise to the main model and replaces pi's full skill list with a compact selected-skill list
2. model-router — Switches the active model role based on task complexity
3. short-circuit — Skips the side model entirely on trivial acknowledgments (好的 / ok / はい), avoiding the per-turn latency and cost

All three modules can be independently toggled on/off.

Why model-router is disabled by default

Model-router switches the active model role based on task complexity. This is a persistent pi model change, the same kind of state change as selecting a model manually, so subsequent turns continue on the routed model until something changes it again.

This can:

• Break prompt caching: Different models don't share cache, causing cache write costs on each switch
• Increase API costs: Frequent model switching adds ~118% overhead in typical workloads
• Reduce performance: Cache misses mean re-uploading system prompt and tools each time

We recommend keeping model-router disabled unless you specifically need it. Enable it via:

/scout:model-router on        # Temporary (current session)

Or add to settings.json for persistent enablement:

{
  "scout": {
    "modules": {
      "modelRouter": true
    }
  }
}

Short-circuit layer

Short-circuit is a cost/latency optimization that lets scout skip the side model entirely on trivial acknowledgments. It mirrors OpenHuman's hybrid-gate pattern: cheap signals handle the obvious cases, the side model only handles the ambiguous middle — so there is no quality loss.

Trivial acknowledgment — a short prompt that is entirely an ack (好的 / ok / はい / 네) routes to "no skills, no role change". Matched against a built-in 中/英/日/韓 phrase table. A trivial ack settles every module, so this is safe even with model-router on. Long prompts are never treated as acks even if they start with an ack word, so 好的，那我们重构整个模块 always reaches the side model.

Anything that isn't a trivial ack falls through to the side model — that's what the model is for. When short-circuit fires, the status bar shows ✓ scout: (skipped) trivial ack for transparency.

How it works

User sends prompt
    │
    ▼
before_agent_start hook fires
    │
    ├─ [short-circuit] Trivial ack? → decide instantly, skip the side model
    │     (status shows "✓ scout: (skipped) …")
    │
    ├─ otherwise → Side agent (cheap model) analyzes prompt + available skills + current role
    ├─ Returns: { skills: [...], role: "...", reasoning: "..." }
    │
    ├─ [skill-router] Replaces pi's full skill list with selected skill metadata
    │     (the main model can then read the selected skill file when needed)
    └─ [model-router] Switches the active model if a different role is recommended

Dependencies

• @d3ara1n/pi-model-roles — model role resolution

Installation

pi install npm:@d3ara1n/pi-model-roles
pi install npm:@d3ara1n/pi-scout

Or add to ~/.pi/agent/settings.json:

{
  "extensions": [
    "/absolute/path/to/pi-extensions/packages/pi-model-roles",
    "/absolute/path/to/pi-extensions/packages/pi-scout"
  ]
}

Configuration

Edit ~/.pi/agent/settings.json:

{
  "scout": {
    "enabled": true,
    "sideAgentRole": "fast",
    "maxSelectedSkills": 5,
    "modules": {
      "skillRouter": true,
      "modelRouter": false,
      "shortCircuit": true
    },
    "shortCircuit": {
      "trivialAck": true,
      "maxAckLength": 12,
      "ackPhrases": ["收到啦", "will do"]
    }
  }
}

| Field | Default | Description | |-------|---------|-------------| | enabled | true | Global on/off | | sideAgentRole | "utility" | pi-model-roles role for the side agent | | maxSelectedSkills | 5 | Max skills the side agent can select; 0 means unlimited. Negative values are normalized to 0 | | modules.skillRouter | true | Enable/disable skill routing | | modules.modelRouter | false | Enable/disable model routing (disabled by default to avoid cache inefficiency and extra costs) | | modules.shortCircuit | true | Enable/disable the short-circuit layer | | shortCircuit.trivialAck | true | Enable the trivial-acknowledgment rule | | shortCircuit.maxAckLength | 12 | Max prompt length (chars) for the trivial-ack rule | | shortCircuit.ackPhrases | [] | Extra ack phrases merged on top of the built-in 中/英/日/韓 table |

Commands

| Command | Description | |---------|-------------| | /scout | Show scout status and last decision | | /scout:skill-router on/off | Toggle skill-router module | | /scout:model-router on/off | Toggle model-router module | | /scout:short-circuit on/off | Toggle short-circuit module |

Performance

Side agent adds ~0.5–2s latency per non-short-circuited turn. The prompt asks the side agent for compact JSON, but the current implementation does not enforce a hard output-token cap; malformed or oversized output is rejected and the main turn continues without applying that decision.

License

MIT